clk: Check for failure at clk_change_rate

The clock rate set could fail, thus check for failure and abort clock rate
change in case the clk_set_rate fails.

Change-Id: I3a3a03f8c0c261b1f89c33e1247e3dbf889a8d26
Signed-off-by: Taniya Das <tdas@codeaurora.org>