clk: qcom: update post div bits to be cleared for MMCC/GPU clocks

MMCC and GPU clocks needs the post div bits to be cleared, so that the
clock measure does not account for any previously set div values in the
debug mux.

Change-Id: I1123e566740518e287692797fa3ab6b316da3bf1
Signed-off-by: Taniya Das <tdas@codeaurora.org>