clk: renesas: cpg-mssr: Add support to restore core clocks during resume

On R-Car Gen3 systems, PSCI system suspend powers down the SoC, possibly
losing clock configuration.  Hence add a notifier chain that can be used
by core clocks to save/restore clock state during system suspend/resume.

The implementation of the actual clock state save/restore operations is
clock-specific, and to be registered with the notifier chain in the SoC
or family-specific cpg_mssr_info.cpg_clk_register() callback.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Tested-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>

drivers/clk/renesas/renesas-cpg-mssr.h

@@ -127,7 +127,8 @@ struct cpg_mssr_info {
 	struct clk *(*cpg_clk_register)(struct device *dev,
 					const struct cpg_core_clk *core,
 					const struct cpg_mssr_info *info,
-					struct clk **clks, void __iomem *base);
+					struct clk **clks, void __iomem *base,
+					struct raw_notifier_head *notifiers);
 };
 
 extern const struct cpg_mssr_info r8a7743_cpg_mssr_info;