brcm47xx/image: build Belkin F7DXXXX images

F7D3302/F7D7302, F7D3301/F7D7301, and F7D4301
brcm47xx/lzmaloader: add Belkin F7DXXXX support

F7D3301/F7D7301, F7D3302/F7D7302 and F7D4301 all have replacements for
the TRX magic ("HDR0"), and all those models also appear to support a
single "QA" TRX magic. Add all of this to the lzmaloader's trx
recognition code.
brcm47xx/mtd-partition: recognize Belkin F7DXXXX TRX headers

F7D3301/F7D7301, F7D3302/F7D7302, and F7D4301 replace the "HDR0" with a
custom byte sequence (which appears to be a date). Also, they all
appear to support a single "QA" byte sequence. Add all of these to the
partition detection.
brcm47xx: fix netconfig for inverted vlan?ports in nvram

This was observed on the Belkin Share F7D7302.