xhci_pme_quirk() is only used when CONFIG_PM is defined.
Compiling a kernel without PM complains about this function

[reworded commit message -Mathias]
Cc: <stable@vger.kernel.org>
Signed-off-by: NTomer Barletz <barletz@gmail.com>
Signed-off-by: NMathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>