USB: xhci: Wait for controller to be ready after reset.

After software resets an xHCI host controller, it must wait for the
"Controller Not Ready" (CNR) bit in the status register to be cleared.
Software is not supposed to ring any doorbells or write to any registers
except the status register until this bit is cleared.

Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>