msm: usb_bam: Fix null pointer reference in connect_pipe

This change fixes a potential null pointer reference issue.

The sps_pipes array should hold references to allocated pipes.
But in connect_pipe, after the pipe is allocated, the reference
to the pipe is not saved in this array. So the array will always
hold NULL pointers. If a code will try to access a pipe reference
stored in this array, it will crash.

Change-Id: I166ce7b5506eeed99f0dfd65beb7db1e97a5d2e0
Signed-off-by: Amit Blay <ablay@codeaurora.org>