ARM: shmobile: Remove the ARCH_SHMOBILE Kconfig symbol

All drivers for Renesas ARM SoCs have gained proper ARCH_RENESAS
platform dependencies.  Hence finish the conversion from ARCH_SHMOBILE
to ARCH_RENESAS for Renesas 32-bit ARM SoCs, as started by commit
9b5ba0df ("ARM: shmobile: Introduce ARCH_RENESAS").

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>