leds: aw2013_led: enable regulators to fix failure when light led

The suspend routine releases all the regulators acquired by the
driver if no LED is enabled. However, this causes an issue when
later the user-space tries to enable the LED. Add a check for
this effect in blinking routine to check if regulators are
disabled and then enable them in case they are.

Change-Id: Id0ee80f37bc779cb3cbe4f1291ece92d59efdf6f
Signed-off-by: Mao Li <maol@codeaurora.org>