msm: ipa: Fix accessing coal registers when clock is off

There is a possibility to access coal registers when the clock
is off which results in unknown behavior. Make changes to ensure
clock is on when accessing coal registers.

Change-Id: Ia13841c5543798cb47ed6953a5c714e7426cb180
Signed-off-by: Chaitanya Pratapa <cpratapa@codeaurora.org>