[media] s5p-cec: mark PM functions as __maybe_unused again

[media] s5p-cec: mark PM functions as __maybe_unused again

A bugfix removed the two callers of s5p_cec_runtime_suspend
and s5p_cec_runtime_resume, leading to the return of a harmless
warning that I had previously fixed in commit aee8937089b1
("[media] s5p_cec: mark suspend/resume as __maybe_unused"):

staging/media/s5p-cec/s5p_cec.c:234:12: error: ‘s5p_cec_runtime_suspend’ defined but not used [-Werror=unused-function]
staging/media/s5p-cec/s5p_cec.c:242:12: error: ‘s5p_cec_runtime_resume’ defined but not used [-Werror=unused-function]

This adds the __maybe_unused annotations to the function that
were not removed and that are now unused when CONFIG_PM
is disabled.

Fixes: 57b978ada073 ("[media] s5p-cec: fix system and runtime PM integration")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>