staging: most: usb: change return value of function drci_rd_reg

staging: most: usb: change return value of function drci_rd_reg

This patch makes function drci_rd_reg return 0 in case of success
and a negative number else. As no caller is evaluating the number
of bytes transferred by function usb_control_msg this information is
being omitted.

Signed-off-by: Christian Gromm <christian.gromm@microchip.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/1590570387-27069-4-git-send-email-christian.gromm@microchip.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>