Fixes the following W=1 kernel build warning(s):

 drivers/usb/gadget/udc/max3420_udc.c: In function ‘max3420_handle_setup’:
 drivers/usb/gadget/udc/max3420_udc.c:626:5: warning: variable ‘addr’ set but not used [-Wunused-but-set-variable]
 626 | u8 addr;
 | ^~~~

Cc: Felipe Balbi <balbi@kernel.org>
Cc: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Acked-by: Jassi Brar <jaswinder.singh@linaro.org>
Link: https://lore.kernel.org/r/20200706133341.476881-24-lee.jones@linaro.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>