bmips: dts: nand: add missing address/size cells

bmips: dts: nand: add missing address/size cells

Fixes the following warnings for Netgear DGND3700v2 and Comtrend VR-3032u:
[    1.059540] 7 fixed-partitions partitions found on MTD device brcmnand.0
[    1.066570] OF: Bad cell count for /ubus/nand@10000200/nandcs@0/partitions
[    1.073766] OF: Bad cell count for /ubus/nand@10000200/nandcs@0/partitions
[    1.081927] OF: Bad cell count for /ubus/nand@10000200/nandcs@0/partitions
[    1.089128] OF: Bad cell count for /ubus/nand@10000200/nandcs@0/partitions

Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>