staging: most: usb: init return value in default path of switch/case expression

This patch avoids returning an uninitialized value in the default
path of the switch expression.

Signed-off-by: Christian Gromm <christian.gromm@microchip.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/1590669703-20004-1-git-send-email-christian.gromm@microchip.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>