usb: usb_bam: Cleanup code and handle error case

This change uses local variable data_fifo instead of global
one which is used with DBM configuration for BAM2BAM data
communication. It also handles error case where pipe is null
still resuming usb device controller.

Change-Id: I912c3fa0ed6a6a31d4a2821c6bb00baf846f0920
Signed-off-by: Mayank Rana <mrana@codeaurora.org>