ASoC: msm: qdp6v2: Support 7.1 channel in Proxy

Increase proxy buffering to support 7.1
channels in Proxy. This is required
to support 7.1 WiFi display

CRs-Fixed: 634644
Change-Id: I735754b2c534f304d6b3fd9782e826bd7d5308b4
Signed-off-by: Alexy Joseph <alexyj@codeaurora.org>