Fix silly mistake when enabling runtime PM support for the Tegra XHCI
driver. If runtime PM was enabled correctly for the XHCI device, then
we should call pm_runtime_get_sync() to enable the device.

Fixes: ee9e5f4c ("usb: xhci: tegra: Add runtime PM support")
Signed-off-by: NJon Hunter <jonathanh@nvidia.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>