MLK-23844-1: ARM64: dts: freescale: imx8mn-ddr4-evk: cleanup Rhom pmic

MLK-23844-1: ARM64: dts: freescale: imx8mn-ddr4-evk: cleanup Rhom pmic

Inculding below cleanup for BD71847 pmic driver:

  --Remove ldo4 which's not used by board, otherwise,ldo4 will be on
    since it's always_on.
  --Remove buck5 which's not used by board too,although that may be off
    by kernel requlator common framework after kernel bootup.
  --Add dvs-run-voltage/dvs-idle-voltage setting for buck2 as i.mx8mm.

Signed-off-by: Robin Gong <yibin.gong@nxp.com>
Reviewed-by: Jacky Bai <ping.bai@nxp.com>