ARM: shmobile: Move definition of shmobile_init_late() to header

The role of the only function in the common.c file in
arch/arm/mach-shmobile, shmobile_init_late(), is to call two
initializers whose definitions depend on kernel configuration
options.  Those initializers may very well be called from a static
inline function in arm/mach-shmobile/include/mach/common.h,
though, in which makes the code a bit easier to read.  Moreover,
the common.c may be dropped entirely then.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Magnus Damm <damm@opensource.se>