sh: propagate r_clk

Make sure the 32 KHz r_clk rate gets propagated correctly. Without
this fix the clocks for RTC, CMT, KEYSC and RWDT are stuck at 0 Hz.

Signed-off-by: Magnus Damm <damm@igel.co.jp>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>