video/stifb.c: make 2 functions static

This patch makes the following needlessly global functions static:
 - stifb_init_fb()
 - stifb_init()

Signed-off-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>