viafb: iface.c, iface.h, ioctl.c, ioctl.h

iface.c, iface.h: support getting video memory from backdoor.
ioctl.c, ioctl.h: support user mode application with additional information

Signed-off-by: Joseph Chan <josephchan@via.com.tw>
Cc: Krzysztof Helt <krzysztof.h1@poczta.fm>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>