ARM: mach-shmobile: AG5 clock framework improvements

This patch improves the state of the AG5 clock
framework support. The main clock parent is
automatically detected, but most of the clocks
are not used by any driver or subsystem at this
point. More work is needed for support of multi
media hardware such as FSI and/or LCDC/MIPI-DSI.

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