MIPS: BCM47XX: Print board name in /proc/cpuinfo

Do not print the constant system type "Broadcom BCM47XX" but print the
name of the actual SoC in use and the detected board.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/5839/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>