sh: sh7786 clkdev lookups.

This plugs in clkdev lookups for the SH7786 clocks and migrates off of
clock string usage for the TMU clocks.

Previously the TMU clocks were aliased to the peripheral clock, so this
gets the driver actually toggling the proper clocks now as well.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>