usb: gadget: FunctionFS: dereference ffs_dev conditionally
usb: gadget: FunctionFS: dereference ffs_dev conditionally

ffs_dev->ffs_release_dev_callback should be accessed only if ffs_dev
is not NULL.

Acked-by: Michal Nazarewicz <605208d9b4c769ca62e9f9f8b592c9cd465fe6d7@mina86.com>
Signed-off-by: Andrzej Pietrasiewicz <0bcd4dade8bc9135441847460b651a5ef589ec79@samsung.com>
Signed-off-by: Felipe Balbi <94dddeeef08b001e003cce128ddc162a4e2c6cd2@ti.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs