usb: msm_otg: add a support for vdd minimization gpio

Add a support to add a dedicated gpio to platform data that will allow
vdd minimization during peripheral suspend. This gpio is used to pullup
the D+ line during suspend, therefore allowing PHY to go to retention mode
and vdd minimization.

Change-Id: I65b287ba1ccbafbd1186677c88204f53e6b9a210
Signed-off-by: Ido Shayevitz <idos@codeaurora.org>