ASoC: msm: Increase Proxy buffering

-Proxy buffering can overflow if BT playback setup takes
longer than usual.
-Fix this by increasing the proxy buffer size so that
we will end up buffering the additional data that can come
in during this time.

Change-Id: I5d091ff12036a80dbf50fd14556b13852dd0cc24
CRs-Fixed: 547254
Signed-off-by: Amit Shekhar <ashekhar@codeaurora.org>