riscv: dts: starfive: jh7110-common: Fix lower rate of CPUfreq by setting PLL0 rate to 1.5GHz

CPUfreq supports 4 cpu frequency loads on 375/500/750/1500MHz.
But now PLL0 rate is 1GHz and the cpu frequency loads become
250/333/500/1000MHz in fact.

The PLL0 rate should be default set to 1.5GHz and set the
cpu_core rate to 500MHz in safe.

Fixes: e2c510d6 ("riscv: dts: starfive: Add cpu scaling for JH7110 SoC")
Signed-off-by: Xingyu Wu <xingyu.wu@starfivetech.com>
Reviewed-by: Hal Feng <hal.feng@starfivetech.com>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>