DWC3: Enable XHCI host in OTG mode

DWC3 has three kind of registers and initilization sequences:
Global, Host and Device. When switching DWC3 roles in OTG mode
from A to B, or B to A, software needs to reinitialization some
Global registers (Event Buffers) and as well as reinitialize
ep0in/out endpoints when switching to peripheral mode.
Host mode requires OTG driver to set PortPowerControl IN OSTS
register only after XHCI drivers sets the same in PORTSC.

Change-Id: I9bc29e00e31d68c0834b6c93896d38267f317c0c
Signed-off-by: Manu Gautam <mgautam@codeaurora.org>