power: extcon:convert extcon lock to spinlock from mutex

power: extcon:convert extcon lock to spinlock from mutex

use spinlock instread of mutex to avoid kernel warning "sleeping
function called from invalid context" if CONFIG_DEBUG_ATOMIC_SLEEP
(sleep inside atomic section checking config) enabled and usb cable
plugged/unplugged.

Bug 1522398

Change-Id: I813f959dc5cb3ce666794a8d57152b6f562046a6
Signed-off-by: Venkat Reddy Talla <vreddytalla@nvidia.com>
Reviewed-on: http://git-master/r/421988
(cherry picked from commit dbca4e0d9f5cdd7da5270288bf1e8add4e164e6a)
Reviewed-on: http://git-master/r/422555
GVS: Gerrit_Virtual_Submit
Reviewed-by: Laxman Dewangan <ldewangan@nvidia.com>