msm: board-msm7627a: Disable GDFS power mode when the USB is connected

Vote against GDFS power mode, when the USB is connected on 8x25.
Currently GDFS power mode is allowed when the USB is connected and
the mode latency set to "500usec's". While data transfer is
happening, GDFS shouldn't be allowed as there is chance of missing
some usb interrupts, which might lead to system instability.

Change-Id: I51ff494ef75c524339e3f9d36bcd54531cc443fb
Signed-off-by: Murali Nalajala <mnalajal@codeaurora.org>