usb: gadget: cdev: Don't use spinlock with sleeping functions

Commit c99a841d ("usb: gadget: cdev: Add spinlock to synchronize
ports->cbits_updated")added spinlock to synchronize ports->cbits_updated
which is calling a sleeping function(put_user) after spinlock is held.

Fix this by protecting just variable, ports->cbits_updated.

Change-Id: I0a52a88344c449c9485f41b871cc97e54b4bf3ca
Signed-off-by: Pratham Pratap <quic_ppratap@quicinc.com>