msm: ipa3: Adding chnages to update event RP from DDR

In suspend scenario while checking channel empty scenario
updating the event ring RP pointer from direct register, it
may cause mismatch in reading in polling context. To avoid
discrepancy  reading RP pointer DDR location.

Change-Id: Ie198ea9ace033e31463acd974f10dccdcac45c55
Signed-off-by: Ashok Vuyyuru <avuyyuru@codeaurora.org>