usb: xhci: Fix build warning seen with CONFIG_PM=n

usb: xhci: Fix build warning seen with CONFIG_PM=n

[ Upstream commit 6056a0f8ede27b296d10ef46f7f677cc9d715371 ]

The following build warning is seen if CONFIG_PM is disabled.

drivers/usb/host/xhci-pci.c:498:13: warning:
	unused function 'xhci_pci_shutdown'

Fixes: f2c710f7dca8 ("usb: xhci: only set D3hot for pci device")
Cc: Henry Lin <henryl@nvidia.com>
Cc: stable@vger.kernel.org	# all stable releases with f2c710f7dca8
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Acked-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20191218011911.6907-1-linux@roeck-us.net
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>