msm: camera: correct op_pixel_clk value

1) The op_pixel_clk is higher than the actual output rate,
when vfe get the value and set the same for vfe clk, it
set to higher frequency which will draw more power.
2) The timing issue is due to the vfe timing requirement
for blanking time. Since we reduce the vfe clk, the
blanking lines required more to meet the minimum
requirement.

Change-Id: I27d781d6524bfae007d00c20d6d60d2e0582543f
Signed-off-by: Hody Hung <hhung@codeaurora.org>