usb: u_bam_data: increase data rx queue size

The hardware controller can actually serve a larger number of requests at
once. This will reduce the overhead of queueing the requests to the
endpoint and improve cpu usage noticably while consuming only slightly
more memory.

Change-Id: Ided9ef4d266b7ec61a514442b8926f29f7edf5bc
Signed-off-by: Gilad Broner <gbroner@codeaurora.org>