ARM: rmobile: Add R-Car Generation 4 support

This adds R-Car Generation 4 (Gen4) support as Renesas ARM64 SoC.

In this version, reusing R-Car Gen3 lowlevel initialize routine [1]
and R-Car Gen3 memory map tables [2] .

[1] arch/arm/mach-rmobile/lowlevel_init_gen3.S
[2] arch/arm/mach-rmobile/memmap-gen3.c

Reviewed-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
Signed-off-by: Hai Pham <hai.pham.ud@renesas.com>
Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
[Marek: - Enable DTO support by default
        - Sort the Kconfig lists
	- Select RCAR_64 Kconfig option to pull in all the shared
	  Kconfig options with Gen3, and use where applicable to
	  deduplicate entries.
	- Fix reference [2] typo in commit message
	- Drop config options moved to Kconfig, rename rest to CFG_
	  accordingly to synchronize with upstream changes. Drop
	  removed CONFIG_VERY_BIG_RAM.
        - Move board size limit to arch/Kconfig
	- Move GICR_BASE to headers instead of common config]
diff --git a/Kconfig b/Kconfig
index 7a8c190..f24e4f0 100644
--- a/Kconfig
+++ b/Kconfig
@@ -427,7 +427,7 @@
 
 config BUILD_TARGET
 	string "Build target special images"
-	default "u-boot-elf.srec" if RCAR_GEN3
+	default "u-boot-elf.srec" if RCAR_64
 	default "u-boot-with-spl.bin" if ARCH_AT91 && SPL_NAND_SUPPORT
 	default "u-boot-with-spl.bin" if MPC85xx && !E500MC && !E5500 && !E6500 && SPL
 	default "u-boot-with-spl.imx" if ARCH_MX6 && SPL
@@ -446,14 +446,14 @@
 
 config HAS_BOARD_SIZE_LIMIT
 	bool "Define a maximum size for the U-Boot image"
-	default y if RCAR_GEN3
+	default y if RCAR_64
 	help
 	  In some cases, we need to enforce a hard limit on how big the U-Boot
 	  image itself can be.
 
 config BOARD_SIZE_LIMIT
 	int "Maximum size of the U-Boot image in bytes"
-	default 1048576 if RCAR_GEN3
+	default 1048576 if RCAR_64
 	depends on HAS_BOARD_SIZE_LIMIT
 	help
 	  Maximum size of the U-Boot image. When defined, the build system