XFree (and X.org) has both always been broken in their conversion of the DPMS
blanking mode when passing to the kernel ioctl FBIOBLANK (in fbdev mode).

This patch makes sure that at least the value passed by userland stays in the
legal range, which has the side effect that an X DPMS POWERDOWN request will
result as an fbdev VESA_POWERDOWN request at the fbdev level now, instead of
an out-of-range value.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>