fbdev: use framebuffer_release() for freeing fb_info structures

Use the framebuffer_release() for freeing fb_info structures allocated
with framebuffer_alloc().

Signed-off-by: Krzysztof Helt <krzysztof.h1@wp.pl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>