sh: clkfwk: Kill off clk_recalc_rate().

The only user for this is the SH-Mobile r_clk, which is now added as a
root clock and can be kicked via propagate_rate() as usual. Given that,
there is no longer any need for the special clk_recalc_rate(), so we kill
it off.

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