ARM: dts: imx6: rename node name flash to eeprom

ARM: dts: imx6: rename node name flash to eeprom

Rename node name flash to eeprom to fix below CHECK_DTBS warnings:
arch/arm/boot/dts/nxp/imx/imx6q-b450v3.dtb: flash@0 (atmel,at25): $nodename: 'anyOf' conditional failed, one must be fixed:
        'flash@0' does not match '^eeprom@[0-9a-f]{1,2}$'
        'flash@0' does not match '^fram@[0-9a-f]{1,2}$'

Signed-off-by: Frank Li <Frank.Li@nxp.com>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>