msm: ipa: fix for data path stall

A previous optimization to aggregate the replenish trigger
introduced a bug in the fifo empty recovery procedure that
can cause a permanent stall. This commit fixes that bug.
Also lower the trigger threshold to 1/8 to make the fifo
empty condition less likely.

Change-Id: I10bf227826328351ee845077e4ceec47b060ce41
Signed-off-by: Ravi Gummadidala <rgummadi@codeaurora.org>