ARM: shmobile: R-Car Gen2: CONFIG_ARCH_SHMOBILE_MULTI is always set

Since commit e042681894b62d60 ("ARM: shmobile: r8a7790: Remove legacy
code"), all R-Car Gen2 SoCs are supported by multiplatform kernels only.
As CONFIG_ARCH_SHMOBILE_MULTI is always set for shmobile multiplatform
kernels, we can remove related #ifdefs in code specific to R-Car Gen2
SoCs.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>