usb: gadget: udc: renesas_usb3: move pm_runtime_{en,dis}able()

This patch moves pm_runtime_{en,dis}able() call timing to
renesas_usb3_{probe,remove}() for supporting PM_SLEEP feature in
the future.

Signed-off-by: Kazuya Mizuguchi <kazuya.mizuguchi.ks@renesas.com>
[shimoda: Revise the commit log]
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>