usb: fsl: Check memory resource before releasing it

[ Upstream commit bc1e3a2d ]

Check memory resource existence before releasing it to avoid NULL
pointer dereference

Signed-off-by: Nikhil Badola <nikhil.badola@freescale.com>
Reviewed-by: Ran Wang <ran.wang_1@nxp.com>
Reviewed-by: Peter Chen <peter.chen@nxp.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>