media: s2255: Use refcount_t instead of atomic_t for num_channels

[ Upstream commit 6cff72f6bcee89228a662435b7c47e21a391c8d0 ]

Use an API that resembles more the actual use of num_channels.

Found by cocci:
drivers/media/usb/s2255/s2255drv.c:2362:5-24: WARNING: atomic_dec_and_test variation before object free at line 2363.
drivers/media/usb/s2255/s2255drv.c:1557:5-24: WARNING: atomic_dec_and_test variation before object free at line 1558.

Link: https://lore.kernel.org/linux-media/20240429-fix-cocci-v3-11-3c4865f5a4b0@chromium.org


Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
(cherry picked from commit 32f2f5385eefa73aaebefda419147ac8599ba9e6)
Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>