ARM: shmobile: r8a7779: move global functions to r8a7779.h

There is no reason each CPU's own function has to exist in common.h.
r8a7779_xxx() go to r8a7779.h

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Acked-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>