arm64: Add Broadcom Set Top Box Kconfig entry point

Add an ARCH_BRCMSTB Kconfig symbol which allows us not to update the
dependencies for all STB-related drivers. Select BRCMSTB_L2_IRQ and
GENERIC_IRQ_CHIP which are required for proper functioning.
Signed-off-by: NDoug Berger <opendmb@gmail.com>
Signed-off-by: NFlorian Fainelli <f.fainelli@gmail.com>
Signed-off-by: NMarkus Mayer <mmayer@broadcom.com>

arch/arm64/Kconfig.platforms

@@ -42,6 +42,13 @@ config ARCH_BERLIN
 	help
 	  This enables support for Marvell Berlin SoC Family
 
+config ARCH_BRCMSTB
+	bool "Broadcom Set-Top-Box SoCs"
+	select BRCMSTB_L2_IRQ
+	select GENERIC_IRQ_CHIP
+	help
+	  This enables support for Broadcom's ARMv8 Set Top Box SoCs
+
 config ARCH_EXYNOS
 	bool "ARMv8 based Samsung Exynos SoC family"
 	select COMMON_CLK_SAMSUNG