clk: clock-rpm: Remove unnecessary clk ops

clk_set_rate and clk_round_rate have been refactored to
"do the right thing" for clocks which only support one rate. Remove
the unnecessary per-clock ops for plls and rpm clocks.

Change-Id: I90fae223004ede17ed5403909fad5c9b0272d884
Signed-off-by: Patrick Daly <pdaly@codeaurora.org>