Usb: Gadget: u_bam_data: Fix NULL ptr dereference in b2b_data_connect_work

During device suspend, bam_data_disconnect disables the usb endpoints
and free the usb request lead to racing. As a part of device resume
bam_data_connect_work dereferences usb request causing NULL pointer
dereference.Fix these by add spinlock.

CRs-Fixed: 1068378
Change-Id: I89aeebecb9c7a277a9e8cc63de963dd67851aeae
Signed-off-by: Arumuga Durai A <cadurai@codeaurora.org>