msm: kgsl: Don't populate the OPP table if it already exists

If we query the OPP table when it doesn't exist we get an error. If
we populate it again with the same operating points we get an error.
So just skip the table create if it already exists and go with
whatever we have.

Change-Id: Ic0dedbad3d5bd24b35867a82873a6ece555d8314
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>