ARM: dts: BCM5301X: Switch Luxul XWC-1000 to the new fixed partitions syntax

This new syntax is slightly better designed & uses "compatible" string.
For details see Documentation/devicetree/bindings/mtd/partition.txt .

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>