ARM: dts: r8a7743: Add OPP table for frequency scaling

Add needed information inside CPU0 for the generic cpufreq-cpu0 driver.

- clock-latency = 300 us
Approximate worst-case latency to do clock transition for every
OPPs. Using an arbitrary safe value similar to r8a7791(R-Car M2) Soc.

- operating-points = < kHz - uV >
List of 6 operating points. All of them are using the same voltage
since DVS is not supported in RZ/G1 Soc.

Note:This also fixes the below errors seen on kernel logs
[    0.876877] cpu cpu0: dev_pm_opp_get_opp_count: OPP table not found (-19)
[    0.883727] cpu cpu1: cpufreq_init: failed to get clk: -2
Signed-off-by: Biju Das <biju.das@bp.renesas.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

arch/arm/boot/dts/r8a7743.dtsi

@@ -38,8 +38,17 @@ cpu0: cpu@0 {
 			reg = <0>;
 			clock-frequency = <1500000000>;
 			clocks = <&cpg CPG_CORE R8A7743_CLK_Z>;
+			clock-latency = <300000>; /* 300 us */
 			power-domains = <&sysc R8A7743_PD_CA15_CPU0>;
 			next-level-cache = <&L2_CA15>;
+
+			/* kHz - uV - OPPs unknown yet */
+			operating-points = <1500000 1000000>,
+					   <1312500 1000000>,
+					   <1125000 1000000>,
+					   < 937500 1000000>,
+					   < 750000 1000000>,
+					   < 375000 1000000>;
 		};
 
 		cpu1: cpu@1 {