Fix accidental USB port resets by GPIO on Zynq/Zedboard boards

The Zynq/Zedboard GPIO driver attempts to tri-state all GPIO pins on
boot up but the order in which I reset the hardware can cause the pins
to be briefly held low before being tri-stated. This is a problem on
boards that use GPIO pins to reset devices.

In particular, the Zybo and ZC-706 boards use a GPIO pin as a USB PHY
reset. If U-boot enables the USB port before booting the kernel, the
GPIO driver attach causes a glitch on the USB PHY reset and the USB
port loses power. My fix is to have the GPIO driver leave the pins in
whatever configuration U-boot placed them.

PR: 225713
Submitted by: Thomas Skibo <thoma555-bsd@yahoo.com>
MFC after: 1 week