usb: roles: Add fwnode_usb_role_switch_get() function

The fwnode_usb_role_switch_get() function is exactly the
same as usb_role_switch_get(), except that it takes struct
fwnode_handle as parameter instead of struct device.

Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Tested-by: Biju Das <biju.das@bp.renesas.com>
Link: https://lore.kernel.org/r/1567070558-29417-8-git-send-email-chunfeng.yun@mediatek.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>