UPSTREAM: usb: raw-gadget: fix null-ptr-deref when reenabling endpoints

Currently we preassign gadget endpoints to raw-gadget endpoints during
initialization. Fix resetting this assignment in raw_ioctl_ep_disable(),
otherwise we will get null-ptr-derefs when an endpoint is reenabled.

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Felipe Balbi <balbi@kernel.org>
Bug: 147413187
(cherry picked from commit da39b5ee40bc00ae3edb4ae4e205b10bc52f980e)
Change-Id: I6809cfdeeadf5fda4071a2f088cd525a1640872d
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>