MIPS: BCM47XX: fix detection for some boards
MIPS: BCM47XX: fix detection for some boards

When a nvram reset was performed from CFE, it sometimes does not
contain the productid value in nvram, but it still contains
hardware_version.

Signed-off-by: Hauke Mehrtens <435ddd46dc66c007a1fa20144c823d37e0d23436@hauke-m.de>
Acked-by: Rafał Miłecki <dced371c11179e2cb83b1e305b9d7b15f379452b@gmail.com>
Signed-off-by: John Crispin <be6487f9df4dce44a640672d6c07330104d43593@openwrt.org>
Patchwork: http://patchwork.linux-mips.org/patch/6316/

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs