ARM: shmobile: Allow ARCH_SHMOBILE_MULTI timer configuration

Move the timer configuration bits to allow use in
case of ARCH_SHMOBILE or ARCH_SHMOBILE_MULTI.

The timers all make use of the regular driver model
so they are safe to enable for ARCH_MULTIPLATFORM.

Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>