This patch makes power_on() call optional.  The voltage source can be
provided to some boards using ams369fg06 panel, thus in this case, power
on/off sequence is not necessary.
Signed-off-by: NJingoo Han <jg1.han@samsung.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>