net: thunderx: Support for different LMAC types within BGX

net: thunderx: Support for different LMAC types within BGX

On 88xx all LMACs in a BGX will be in same mode but on 81xx
BGX can be split as two and there can be LMACs configured in
different modes.

These changes move lmac_type, lane2serdes fields into per lmac
struct from BGX struct. Got rid of qlm_mode field which has become
redundant with these changes. And now no of valid LMACs is read
from CSRs configured by low level firmware and figuring out the
same based on QLM mode is discarded

Signed-off-by: Sunil Goutham <sgoutham@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>