msm: board-9615: Fix number of USB BAM connections

This change fixes a mismatch between the USB BAM driver
and the board file, regarding MAX number of USB BAM connections.
This is since USB BAM driver has changed the MAX number of BAM
connections from 4 to 8.

Change-Id: If540a24929fef6ca2d23770a325718a59273d6a1
Signed-off-by: Amit Blay <ablay@codeaurora.org>