console/vgacon.c: mark file-local symbol static

warning: symbol 'vgacon_text_mode_force' was not declared. Should it be static?

Signed-off-by: Thiago Farina <tfransosi@gmail.com>
Acked-by: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>