arm64: dts: layerscape: remove en25s64 and only keep jedec,spi-nor compatible string

arm64: dts: layerscape: remove en25s64 and only keep jedec,spi-nor compatible string

In jedec,spi-nor.yaml:
  SPI NOR flashes compatible with the JEDEC SFDP standard or which may be
  identified with the READ ID opcode (0x9F) do not deserve a specific
  compatible. They should instead only be matched against the generic
  "jedec,spi-nor" compatible.

en25s64 already in drivers/mtd/spi-nor/eon.c. So remove it safely and fix
below warning:
  arch/arm64/boot/dts/freescale/fsl-ls1012a-qds.dtb: flash@2: compatible: 'oneOf' conditional failed, one must be fixed:
        ['en25s64', 'jedec,spi-nor'] is too long

Signed-off-by: Frank Li <[email protected]>
Signed-off-by: Shawn Guo <[email protected]>