ARM: mach-shmobile: Add SDHI support for AG5EVM and sh73a0

Add SDHI0 and SDHI1 support to the AG5EVM board
including platform data, pinmux configuration
and clock bindings.

Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>