msm: ipa: fix for spinlock recursion bug

Upon TX completion, IPA driver invokes a client supplied
callback. This happens with the TX packet list spinlock
held. A client could attempt a TX operation from the callback
causing an attempt to lock the spinlock of the same TX packet
list which is illegal. This change releases the spinlock right
before calling client callback and locks it back right after.

Change-Id: I9cb466515b9e6c71cdb509e795adb3fade4d1b16
Signed-off-by: Ravi Gummadidala <rgummadi@codeaurora.org>