ARM: Rename ARCH_SHMOBILE to ARCH_SHMOBILE_LEGACY

SH-Mobile platforms are transitioning from non-multiplatform to
multiplatform kernel. A new ARCH_SHMOBILE_MULTI configuration symbol has
been created to group all multiplatform-enabled SH-Mobile SoCs. The
existing ARCH_SHMOBILE configuration symbol groups SoCs that haven't
been converted yet.

This arrangement works fine for the arch/ code, but lots of drivers
needed on both ARCH_SHMOBILE and ARCH_SHMOBILE_MULTI depend on
ARCH_SHMOBILE only. In order to avoid changing them, rename
ARCH_SHMOBILE to ARCH_SHMOBILE_LEGACY, and create a new boolean
ARCH_SHMOBILE configuration symbol that is selected by both
ARCH_SHMOBILE_LEGACY and ARCH_SHMOBILE_MULTI.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Acked-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>