clk: msm: Add opp_table_populated flag to the clk struct

In some cases, populate_clock_opp_table may be called multiple
times on the same clk. To accommodate this, add a flag to the
clk struct which keeps track of whether the OPP table of the clk
is populated.

Change-Id: I91682b4d75a39fd757b871bfa74d11568a1655ac
Signed-off-by: Devesh Jhunjhunwala <deveshj@codeaurora.org>