sh: move sh clock.c contents to drivers/sh/clk.

This patch is V2 of the SH clock framework move from
arch/sh/kernel/cpu/clock.c to drivers/sh/clk.c. All
code except the following functions are moved:
clk_init(), clk_get() and clk_put().

The init function is still kept in clock.c since it
depends on the SH-specific machvec implementation.

The symbols clk_get() and clk_put() already exist in
the common ARM clkdev code, those symbols are left in
the SH tree to avoid duplicating them for SH-Mobile ARM.

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