ARM: shmobile: Move common.h

Change location for common.h so it can be used as #include "common.h"
instead of the old style #include <mach/common.h>.

Signed-off-by: Magnus Damm <damm+renesas@opensource.se>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>