media: dvb-usb-remote: fix dvb_usb_nec_rc_key_to_event type mismatch

gcc-11 warns about the prototype not exactly matching the function
definition:

drivers/media/usb/dvb-usb/dvb-usb-remote.c:363:20: error: argument 2 of type ‘u8[5]’ {aka ‘unsigned char[5]’} with mismatched bound [-Werror=array-parameter=]
  363 |                 u8 keybuf[5], u32 *event, int *state)
      |                 ~~~^~~~~~~~~
In file included from drivers/media/usb/dvb-usb/dvb-usb-common.h:13,
                 from drivers/media/usb/dvb-usb/dvb-usb-remote.c:9:
drivers/media/usb/dvb-usb/dvb-usb.h:490:65: note: previously declared as ‘u8[]’ {aka ‘unsigned char[]’}
  490 | extern int dvb_usb_nec_rc_key_to_event(struct dvb_usb_device *, u8[], u32 *, int *);
      |                                                                 ^~~~

Fixes: 776338e1 ("[PATCH] dvb: Add generalized dvb-usb driver")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>