msm: ipa: enable packet dropping for A2 facing IPA end-points

After switching to DMA-BAM based HW bridge between IPA and A2,
bi-directional throughput issues are being observed with the IPA
default head-of-line-blocking behavior. This commit enables IPA
to drop packets when needed to maintain desired bi-directional
throughputs.

Change-Id: I26f74dfed6e4e1f96639249cc13cf2b820161464
Signed-off-by: Ravi Gummadidala <rgummadi@codeaurora.org>