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/arch/arm/mach-rmobile/Kconfig.rcar4 b/arch/arm/mach-rmobile/Kconfig.rcar4
new file mode 100644
index 0000000..6d9e165
--- /dev/null
+++ b/arch/arm/mach-rmobile/Kconfig.rcar4
@@ -0,0 +1,8 @@
+if RCAR_GEN4
+
+choice
+	prompt "Renesas ARM64 SoCs board select"
+	optional
+endchoice
+
+endif