drivers/video/hecubafb.c: make 4 functions static

This patch makes the following needlessly global functions static:
- hcb_wait_for_ack()
- hcb_wait_for_ack_clear()
- apollo_send_data()
- apollo_send_command()

Signed-off-by: Adrian Bunk <bunk@stusta.de>
Cc: Jaya Kumar <jayakumar.lkml@gmail.com>
Cc: Antonino Daplas <adaplas@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>