usb: host: xhci-plat: enable clk in resume timing

This patch enables the clk in resume timing when device_may_wakeup()
is false. Otherwise, kernel panic happens when R-Car resumes the system
from Suspend-to-RAM because the clk is disabled.

Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>