drm/fb-helper: Make docs for fb_set_suspend wrappers consistent

I figured I might as well go ocd and make them booleans and rename the
locked version too.

v2: Review from Noralf.

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Cc: Noralf Trønnes <noralf@tronnes.org>
Fixes: cfe63423 ("drm/fb-helper: Add drm_fb_helper_set_suspend_unlocked()")
Acked-by: Noralf Trønnes <noralf@tronnes.org>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20160823152727.31788-1-daniel.vetter@ffwll.ch