V4L/DVB (6009): Bt8xx: "extern inline" -> "static inline"

"extern inline" will have different semantics with gcc 4.3.

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