ARM: BCM: Enable ARM erratum 798181 for BRCMSTB

Commit 04fcab32 ("ARM: 8111/1: Enable
erratum 798181 for Broadcom Brahma-B15") enables this erratum for
affected Broadcom Brahma-B15 CPUs when CONFIG_ARM_ERRATA_798181=y.
Let's make sure that config option is actually set.
Signed-off-by: Gregory Fong <gregory.0xf0@gmail.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Olof Johansson <olof@lixom.net>

arch/arm/mach-bcm/Kconfig

@@ -140,6 +140,7 @@ config ARCH_BCM_63XX
 config ARCH_BRCMSTB
 	bool "Broadcom BCM7XXX based boards" if ARCH_MULTI_V7
 	select ARM_GIC
+	select ARM_ERRATA_798181 if SMP
 	select HAVE_ARM_ARCH_TIMER
 	select BRCMSTB_GISB_ARB
 	select BRCMSTB_L2_IRQ