mod/clock: Fix erroneous condition checking in set rate function

The create_async_request_set_rate() function creates an event with a
delayed response, returning FWK_PENDING to indicate that the event
was successfully created and the device context updated. Previously,
clock_set_rate() erroneously checked the return value using a
condition that always evaluated to true due to the use of the OR
(||) operator.

This commit fixes the condition so that the debug log is only
triggered if the return value is not FWK_PENDING, ensuring that the
function's behavior correctly reflects the expected return value and
does not produce misleading debug output.

Signed-off-by: Md Golam Tanvir Zim <mdgolamtanvir.zim@arm.com>
Change-Id: Iaa3e0bd2c3937cc3a13a7bb3b7df4a5b75c4d7ba