usb: gadget: u_bam: Release spinlock in case of skb_copy error

gbam_write_data_tohost() was failing to release port_lock_dl
in case skb_copy_expand() failed. Instead of returning, break
out of the loop so the spinlock can be released. Bug was found
with static analysis checker.

Change-Id: Ia4f00ee2f565b03a90b1073ef630f2780e4207e3
Signed-off-by: Jack Pham <jackp@codeaurora.org>