ARM: dts: BCM5301X: Fix nodes names

This fixes following errors for all BCM5301X dts files:
chipcommonA@18000000: $nodename:0: 'chipcommonA@18000000' does not match '^([a-z][a-z0-9\\-]+-bus|bus|soc|axi|ahb|apb)(@[0-9a-f]+)?$'
mpcore@19000000: $nodename:0: 'mpcore@19000000' does not match '^([a-z][a-z0-9\\-]+-bus|bus|soc|axi|ahb|apb)(@[0-9a-f]+)?$'
mdio-bus-mux@18003000: $nodename:0: 'mdio-bus-mux@18003000' does not match '^mdio-mux[\\-@]?'
dmu@1800c000: $nodename:0: 'dmu@1800c000' does not match '^([a-z][a-z0-9\\-]+-bus|bus|soc|axi|ahb|apb)(@[0-9a-f]+)?$'

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