bnxt_en: Initialize "context kind" field for context memory blocks.

If firmware provides the offset to the "context kind" field of the
relevant context memory blocks, we'll initialize just that field for
each block instead of initializing all of context memory.

Populate the bnxt_mem_init structure with the proper offset returned
by firmware.  If it is older firmware and the information is not
available, we set the offset to an invalid value and fall back to
the old behavior of initializing every byte.  Otherwise, we initialize
only the "context kind" byte at the offset.

Reviewed-by: Edwin Peer <edwin.peer@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>