ARM: dts: msm: Add WLAN RX buffer count entry for wcnss

WLAN RX buffer count is a configurable value, using a smaller
count of this buffer will reduce the memory usage.

Change-Id: Ib3b25870392e3348295c57646f9f6a0b8e8a0dc4
CRs-fixed: 636102
Signed-off-by: Hardik Kantilal Patel <hkpatel@codeaurora.org>