arm64: dts: imx8mp-debix-som-a-bmb: Fix EEPROM #size-cells

arm64: dts: imx8mp-debix-som-a-bmb: Fix EEPROM #size-cells

The mac-address is passed as a subnode of the eeprom and its 'reg'
property describe a range of addresses in the eeprom.

Therefore, #size-cells should be set to 1 instead of 0.

This fixes the following schema warnings:

imx8mp-debix-som-a-bmb-08.dtb: eeprom@52: #size-cells:0:0: 1 was expected
	from schema $id: http://devicetree.org/schemas/eeprom/at24.yaml#
imx8mp-debix-som-a-bmb-08.dtb: eeprom@52: mac-address@0:reg: [[0], [12]] is too long
	from schema $id: http://devicetree.org/schemas/eeprom/at24.yaml#
imx8mp-debix-som-a-bmb-08.dtb: eeprom@52: mac-address@c:reg: [[12], [12]] is too long
	from schema $id: http://devicetree.org/schemas/eeprom/at24.yaml#
imx8mp-debix-som-a-bmb-08.dtb: eeprom@52: Unevaluated properties are not allowed ('#address-cells', '#size-cells', 'mac-address@0', 'mac-address@c' were unexpected)
	from schema $id: http://devicetree.org/schemas/eeprom/at24.yaml#

Signed-off-by: Fabio Estevam <festevam@denx.de>
Reviewed-by: Marco Felsch <m.felsch@pengutronix.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>