clk: qcom: osm: Add determine_rate ops for OSM CPU clock driver

Clock rates are stored in unsigned long field, but round_rate
ops returns a long value which is causing to long overflow if
the CPU clock rate exceeds 2GHz, so define the determine_rate ops.

Change-Id: I2c48dc51bdf6be260fb4697012d08237cbba3f21
Signed-off-by: Taniya Das <tdas@codeaurora.org>