arm: Add Khadas VIM support based on Meson GXL family

This adds platform code for the Khadas VIM board based on a
Meson GXL (S905X) SoC with the Meson GXL configuration.

This initial submission supports UART, MMC/SDCard and Ethernet with the
Internal RMII PHY.

The meson-gxl-s905x-khadas-vim.dts is synchronised from the linux 4.13
stable tree as of 4.13.8.

Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
diff --git a/board/amlogic/khadas-vim/README b/board/amlogic/khadas-vim/README
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+U-Boot for Khadas VIM
+=======================
+
+Khadas VIM is an Open Source DIY Box manufactured by Shenzhen Tomato
+Technology Co., Ltd with the following specifications:
+
+ - Amlogic S905x ARM Cortex-A53 quad-core SoC @ 2GHz
+ - ARM Mali 450 GPU
+ - 2GB DDR3 SDRAM
+ - 10/100 Ethernet
+ - HDMI 2.0 4K/60Hz display
+ - 40-pin GPIO header
+ - 2 x USB 2.0 Host, 1 x USB 2.0 Type-C OTG
+ - 8GB/16GBeMMC
+ - microSD
+ - SDIO Wifi Module, Bluetooth
+ - Two channels IR receiver
+
+Currently the u-boot port supports the following devices:
+ - serial
+ - eMMC, microSD
+ - Ethernet
+
+U-Boot compilation
+==================
+
+ > export ARCH=arm
+ > export CROSS_COMPILE=aarch64-none-elf-
+ > make khadas-vim_defconfig
+ > make
+
+Image creation
+==============
+
+Amlogic doesn't provide sources for the firmware and for tools needed
+to create the bootloader image, so it is necessary to obtain them from
+the git tree published by the board vendor:
+
+ > wget https://releases.linaro.org/archive/13.11/components/toolchain/binaries/gcc-linaro-aarch64-none-elf-4.8-2013.11_linux.tar.xz
+ > wget https://releases.linaro.org/archive/13.11/components/toolchain/binaries/gcc-linaro-arm-none-eabi-4.8-2013.11_linux.tar.xz
+ > tar xvfJ gcc-linaro-aarch64-none-elf-4.8-2013.11_linux.tar.xz
+ > tar xvfJ gcc-linaro-arm-none-eabi-4.8-2013.11_linux.tar.xz
+ > export PATH=$PWD/gcc-linaro-aarch64-none-elf-4.8-2013.11_linux/bin:$PWD/gcc-linaro-arm-none-eabi-4.8-2013.11_linux/bin:$PATH
+ > git clone https://github.com/khadas/u-boot -b Vim vim-u-boot
+ > cd vim-u-boot
+ > make kvim_defconfig
+ > make
+ > export FIPDIR=$PWD/fip
+
+Go back to mainline U-Boot source tree then :
+ > mkdir fip
+
+ > cp $FIPDIR/gxl/bl2.bin fip/
+ > cp $FIPDIR/gxl/acs.bin fip/
+ > cp $FIPDIR/gxl/bl21.bin fip/
+ > cp $FIPDIR/gxl/bl30.bin fip/
+ > cp $FIPDIR/gxl/bl301.bin fip/
+ > cp $FIPDIR/gxl/bl31.img fip/
+ > cp u-boot.bin fip/bl33.bin
+
+ > $FIPDIR/blx_fix.sh \
+	fip/bl30.bin \
+	fip/zero_tmp \
+	fip/bl30_zero.bin \
+	fip/bl301.bin \
+	fip/bl301_zero.bin \
+	fip/bl30_new.bin \
+	bl30
+
+ > $FIPDIR/acs_tool.pyc fip/bl2.bin fip/bl2_acs.bin fip/acs.bin 0
+
+ > $FIPDIR/blx_fix.sh \
+	fip/bl2_acs.bin \
+	fip/zero_tmp \
+	fip/bl2_zero.bin \
+	fip/bl21.bin \
+	fip/bl21_zero.bin \
+	fip/bl2_new.bin \
+	bl2
+
+ > $FIPDIR/gxl/aml_encrypt_gxl --bl3enc --input fip/bl30_new.bin
+ > $FIPDIR/gxl/aml_encrypt_gxl --bl3enc --input fip/bl31.img
+ > $FIPDIR/gxl/aml_encrypt_gxl --bl3enc --input fip/bl33.bin
+ > $FIPDIR/gxl/aml_encrypt_gxl --bl2sig --input fip/bl2_new.bin --output fip/bl2.n.bin.sig
+ > $FIPDIR/gxl/aml_encrypt_gxl --bootmk \
+		--output fip/u-boot.bin \
+		--bl2 fip/bl2.n.bin.sig \
+		--bl30 fip/bl30_new.bin.enc \
+		--bl31 fip/bl31.img.enc \
+		--bl33 fip/bl33.bin.enc
+
+and then write the image to SD with:
+
+ > DEV=/dev/your_sd_device
+ > dd if=fip/u-boot.bin.sd.bin of=$DEV conv=fsync,notrunc bs=512 skip=1 seek=1
+ > dd if=fip/u-boot.bin.sd.bin of=$DEV conv=fsync,notrunc bs=1 count=444