msm: ipa: change default low watermark for rx buffers

Change the threshold for resubmitting RX buffers to IPA in case
of allocation errors to a bigger number than 0.
In some corner cases a packet from IPA to AP might be larger than
the side of 1 buffer, which can result in IPA stall if threshold
is 0.

CRs-Fixed: 1027726
Change-Id: Ic841de25597c2cd4ce007823f9b9727e858a73cb
Acked-by: Ady Abraham <adya@qti.qualcomm.com>
Signed-off-by: Skylar Chang <chiaweic@codeaurora.org>