fbcon: cursor blink control

Add sysfs attribute to enable or disable cursor blinking.  This will also
disable cursor blinking if the VT layer's softcursor is active.  These changes
are required to enable some machines to enter low-power states properly.

Signed-off-by: Antonino Daplas <adaplas@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>