On R-Car Gen3 systems, PSCI system suspend powers down the SoC, losing
clock configuration.  Register a notifier to save/restore the RCKCR
register during system suspend/resume.
Signed-off-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Tested-by: NNiklas Söderlund <niklas.soderlund+renesas@ragnatech.se>