usb: ehci-msm2: Add support for resume gpio

Some peripherals cannot wakeup from XO shutdown with in-band resume
signalling. Assert resume gpio before driving resume to bring
peripheral out of XO shutdown and detect usb bus resume.

CRs-Fixed: 497866
Change-Id: I2a277fd232871c07abeeb9035752d59ee13398f8
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>