V4L/DVB (6576): cx88-mpeg.c: make 4 functions static

This patch makes the following needlessly global functions static:
- cx8802_init_common()
- cx8802_fini_common()
- cx8802_suspend_common()
- cx8802_resume_common()

Signed-off-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>