xhci: Platform: Add (en/dis)able_usb3_lpm_timeout

To use auto U0-U1/U2 transition by xhci platform device add
(en/dis)able_usb3_lpm_timeout function to the xhci_plat_xhci_driver struct.

Signed-off-by: Pratyush Anand <pratyush.anand@st.com>
Tested-by: Aymen Bouattay <aymen.bouattay@st.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>