msm:ipa: Race condition observed during client disconnect

Client ep[i] entries are memset to 0 as part of tearing down
uc offload pipes which results in a race condition, if there are already
some packets which have been sent to IPA, when the client notify callback
is called.

Change-Id: I998e5d1c09d82e72b80ff00d1dd96398a92adc75
Signed-off-by: Praveen Kurapati <pkurapat@codeaurora.org>
Signed-off-by: Chaitanya Pratapa <cpratapa@codeaurora.org>