MIPS: BCM47XX: print board name in machine entry in cpuinfo

This will add the board name to the machine entry in /proc/cpuinfo.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Signed-off-by: John Crispin <blogic@openwrt.org>
Patchwork: http://patchwork.linux-mips.org/patch/5864/