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: I2c1142ac38a87bf6e680983eb970c6943eabb88c
Signed-off-by: Amit Blay <ablay@codeaurora.org>