msm: camera: isp: Fix camif raw only snapshot usecase

For camif raw only usecase, user space does not configure reg_update.
Configure it in kernel when epoch irq is received. Currently, frame
skip registers are configured in both epoch irq routine and sof
routine. This causes frame skip not applied properly. Remove it from
sof irq routine.

Change-Id: I54bcc46f461a380d741557c872c795a8bb2f8442
Signed-off-by: Sreesudhan Ramakrish Ramkumar <srramku@codeaurora.org>