power: qpnp-smbcharger: Add a led class device controlled by smbcharger

Register a led class device controlled by smbcharger. It allows four
patterns on the notification LED: Off, Solid On, Blink pattern1
and Blink pattern2.

Change-Id: Ib6d982c317ab82685e37ff09fc3ab2cfc273dfec
Signed-off-by: Chunmei Cai <ccai@codeaurora.org>