arm64: dts: imx8mp-phycore-som: LDO5 needs to be enabled instead of LDO4

LDO4 is not connected so disable it. And LDO5 is used for VSEL of
the NVCC_SD2 SD-Card bus. Having it disabled seems not to have an
impact on the functionality. We enable it, as it is used.

Signed-off-by: Teresa Remmet <t.remmet@phytec.de>
Reviewed-by: Haibo Chen <haibo.chen@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>