msm: msm_bus: Update clock APIs to support rounded rate

To correctly set rates of local clocks, the frequency
value should be rounded up to the supported values before
calling the API to set rate. This patch adds support for
rounding the rate to the supported values.

Change-Id: Id0cdc14121edfedbffce83834f521d8ce67b82f4
Signed-off-by: Gagan Mac <gmac@codeaurora.org>