ARM: versatile: fix versatile_defconfig

With the introduction of CONFIG_ARCH_MULTIPLATFORM, versatile is
no longer the default platform, so we need to enable
CONFIG_ARCH_VERSATILE explicitly in order for that to be selected
rather than the multiplatform configuration.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

arch/arm/configs/versatile_defconfig

+CONFIG_ARCH_VERSATILE=y
 CONFIG_EXPERIMENTAL=y
 # CONFIG_LOCALVERSION_AUTO is not set
 CONFIG_SYSVIPC=y