xen/arm: platform: Add support for R-Car Gen4

Add Rcar Gen4 platform choice to Kconfig to select all required
drivers automatically.

Changelog:
v1 -> v2:
- Added RB from Stefano Stabellini

Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Signed-off-by: Volodymyr Babchuk <volodymyr_babchuk@epam.com>
Signed-off-by: Mykyta Poturai <mykyta_poturai@epam.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>

xen/arch/arm/platforms/Kconfig

@@ -29,6 +29,15 @@ config RCAR3
 	help
 	Enable all the required drivers for Renesas RCar3
 
+config RCAR4
+	bool "Renesas RCar4 support"
+	depends on ARM_64
+	select HAS_SCIF
+	select HAS_ITS
+	select IPMMU_VMSA
+	help
+	Enable all the required drivers for Renesas RCar4
+
 config MPSOC
 	bool "Xilinx Ultrascale+ MPSoC support"
 	depends on ARM_64
@@ -63,4 +72,3 @@ config ALL32_PLAT
 config MPSOC_PLATFORM
 	bool
 	default (ALL64_PLAT || MPSOC)
-