ARM: shmobile: defconfig: Enable r8a7792 SoC

Enable support for r8a7792 SoC in shmobile_defconfig.
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

arch/arm/configs/shmobile_defconfig

@@ -17,6 +17,7 @@ CONFIG_ARCH_R8A7778=y
 CONFIG_ARCH_R8A7779=y
 CONFIG_ARCH_R8A7790=y
 CONFIG_ARCH_R8A7791=y
+CONFIG_ARCH_R8A7792=y
 CONFIG_ARCH_R8A7793=y
 CONFIG_ARCH_R8A7794=y
 CONFIG_ARCH_SH73A0=y