phy: msm: usb: Add USB atomic notifier for USB psy registration

Add support for USB atomic notifier callback when power supply
framework registers any power supply. Check in the callback
function if the psy registered is USB, and then register extcon
handles for VBUS and ID notifications. This helps to remove
dependency between SMB and msm_otg probe routines.

Change-Id: I4d4d98cc45ab70fc3742142a0f18fcfc84bea790
Signed-off-by: Ajay Agarwal <ajaya@codeaurora.org>