bcma: fix handling of big addrl

The return value of bcma_erom_get_addr_desc() is a unsigned value and it
could wrap around in the two complement writing.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
bgmac: bgmac depends on phylib

bgmac is using functions from phylib, add the dependency.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
bgmac: make bgmac work on systems without nvram