ARM: shmobile: r8a7740: add A4S pm domain support

This patch adds basic A4S pm domain support.
Now, below devices can be controled by PM

Common-SHwy, Common-HPB, BSC, MFI, MMFROM, HS-SHwy,
SYS-HPB, INTCA, DBSC, DDRPHY (Logic),
ATAPI, GbEther, AXI-bus

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Acked-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>