bcm53xx: update bcma device tree intergeneration and fix nvram parsing

This fixes lots of sparse and checkpatch errors and extends the 
documentation.

This also fixes a problem in the nvram parser, it now detects the 
correct nvram on my Netgear R6250.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>


git-svn-id: svn://svn.openwrt.org/openwrt/trunk@42272 3c298f89-4303-0410-b956-a3cf2f4a3e73