usb: host: plat: Enable xHCI plat runtime PM

Enable the xHCI plat runtime PM for parent device to suspend/resume
xHCI. Also call pm_runtime_forbid() in probe() function to force users
to explicitly enable runtime pm using power/control in sysfs, in case
some parent devices didn't implement runtime PM callbacks.

[set do_wakeup to true when runtime suspending -Mathias]
Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>