drivers: sh: compile drivers/sh/pm_runtime.c if ARCH_SHMOBILE_MULTI

drivers: sh: compile drivers/sh/pm_runtime.c if ARCH_SHMOBILE_MULTI

If the kernel is built to support multi-ARM configuration with shmobile
support built in, then drivers/sh is not built. This contains the PM
runtime code in drivers/sh/pm_runtime.c, which implicitly enables the
module clocks for all devices, and thus is quite essential.
Without this, the state of clocks depends on implicit reset state, or on
the bootloader.

If ARCH_SHMOBILE_MULTI then build the drivers/sh directory, but ensure that
bits that may conflict (drivers/sh/clk if the common clock framework is
enabled) or are not used (drivers/sh/intc), are not built.
Also, only enable the PM runtime code when actually running on a shmobile
SoCs that needs it.

ARCH_SHMOBILE_MULTI was added a while ago by commit
efacfce5f8a523457e9419a25d52fe39db00b26a ("ARM: shmobile: Introduce
ARCH_SHMOBILE_MULTI"), but drivers/sh was compiled for both
ARCH_SHMOBILE_LEGACY and ARCH_SHMOBILE_MULTI until commit
bf98c1eac1d4a6bcf00532e4fa41d8126cd6c187 ("ARM: Rename ARCH_SHMOBILE to
ARCH_SHMOBILE_LEGACY").

Inspired by a patch from Ben Dooks <ben.dooks@codethink.co.uk>.

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