fbdev: add events for early fb event support

fbdev: add events for early fb event support

Add FB_EARLY_EVENT_BLANK and FB_R_EARLY_EVENT_BLANK event mode supports.
first, fb_notifier_call_chain() is called with FB_EARLY_EVENT_BLANK and
fb_blank() of specific fb driver is called and then
fb_notifier_call_chain() is called with FB_EVENT_BLANK again at
fb_blank().  and if fb_blank() was failed then fb_nitifier_call_chain()
would be called with FB_R_EARLY_EVENT_BLANK to revert the previous
effects.

Signed-off-by: Inki Dae <[email protected]>
Signed-off-by: Kyungmin Park <[email protected]>
Cc: Lars-Peter Clausen <[email protected]>
Acked-by: Florian Tobias Schandinat <[email protected]>
Cc: Richard Purdie <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>