ARM: mach-shmobile: Add eMMC support through MMCIF on AG5EVM

Adding platform resources, PFC setting and release
reset pin for eMMC on ag5evm.

[damm@opensource.se: Add MSTP code for MMCIF]
Signed-off-by: Takashi YOSHII <takashi.yoshii.zj@renesas.com>
Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>