brcm47xx: bgmac: b44: add support for Byte Queue Limits

This adds support for Byte Queue Limits in bgmac and b44, now it is 
possible to use more advanced network queue control algorithms.

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


git-svn-id: svn://svn.openwrt.org/openwrt/trunk@38038 3c298f89-4303-0410-b956-a3cf2f4a3e73