mips: add initial support for qca956x referenced board

QCA9563 is CPU used on AP152 board :

    Clock speed : 750 MHz ,
    Arch :  Mips 74Kc,
    Eth : SGMII interface,
    MIMO config : 3 * 3 450M,
    2 * USB 2.0,

Signed-off-by: Rosy Song <rosysong@rosinson.com>

Changes for v2:
   - coding style cleanup
   - remove ununsed flash chip in defconfig
   - enable automatic icache / dcache size in defconfig

Changes for v3:
   - add detailed information for qca956x in commit message

Changes for v4:
   - remove pre-configured network settings in ap152.h

Changes for v5:
   - coding style cleanup
diff --git a/configs/ap152_defconfig b/configs/ap152_defconfig
new file mode 100644
index 0000000..21cb6eb
--- /dev/null
+++ b/configs/ap152_defconfig
@@ -0,0 +1,49 @@
+CONFIG_MIPS=y
+CONFIG_SYS_TEXT_BASE=0x9F000000
+CONFIG_SYS_MALLOC_F_LEN=0x800
+CONFIG_SYS_CACHE_SIZE_AUTO=y
+CONFIG_DEBUG_UART_BOARD_INIT=y
+CONFIG_DEBUG_UART_BASE=0xb8020000
+CONFIG_DEBUG_UART_CLOCK=25000000
+CONFIG_ARCH_ATH79=y
+CONFIG_TARGET_AP152=y
+CONFIG_DEBUG_UART=y
+CONFIG_BOOTDELAY=3
+CONFIG_USE_BOOTARGS=y
+CONFIG_BOOTARGS="console=ttyS0,115200 root=/dev/mtdblock2 rootfstype=squashfs"
+CONFIG_DISPLAY_CPUINFO=y
+CONFIG_BOARD_EARLY_INIT_F=y
+CONFIG_SYS_PROMPT="ap152 # "
+# CONFIG_CMD_BDI is not set
+# CONFIG_CMD_CONSOLE is not set
+# CONFIG_CMD_ELF is not set
+# CONFIG_CMD_XIMG is not set
+# CONFIG_CMD_EXPORTENV is not set
+# CONFIG_CMD_IMPORTENV is not set
+# CONFIG_CMD_EDITENV is not set
+# CONFIG_CMD_CRC32 is not set
+CONFIG_CMD_MEMTEST=y
+# CONFIG_CMD_FLASH is not set
+CONFIG_CMD_SF=y
+CONFIG_CMD_SPI=y
+CONFIG_CMD_MTDPARTS=y
+CONFIG_MTDIDS_DEFAULT="nor0=spi-flash.0"
+CONFIG_MTDPARTS_DEFAULT="mtdparts=spi-flash.0:256k(u-boot),64k(u-boot-env),6336k(rootfs),1472k(uImage),64k(ART)"
+# CONFIG_ISO_PARTITION is not set
+CONFIG_DEFAULT_DEVICE_TREE="ap152"
+CONFIG_ENV_IS_IN_SPI_FLASH=y
+# CONFIG_NET is not set
+CONFIG_DM_SPI_FLASH=y
+CONFIG_SPI_FLASH=y
+CONFIG_SPI_FLASH_BAR=y
+CONFIG_SPI_FLASH_WINBOND=y
+CONFIG_SPI_FLASH_DATAFLASH=y
+CONFIG_SPI_FLASH_MTD=y
+CONFIG_PINCTRL=y
+CONFIG_DM_SERIAL=y
+CONFIG_DEBUG_UART_SHIFT=2
+CONFIG_SYS_NS16550=y
+CONFIG_SPI=y
+CONFIG_DM_SPI=y
+CONFIG_ATH79_SPI=y
+CONFIG_LZMA=y