bnx2x: downgrade Max BW error message to debug

bnx2x: downgrade Max BW error message to debug

There are valid configurations where Max BW is configured to zero for
some VNs.
Print the message only if debugging is enabled and do not call the
configuration "illegal".

[v2: use DP(), not BNX2X_DBG_ERR(); recommended by Eilon Greenstein.]

(backported from upstream commit 96b0accb8867627250e911f8929e6c01da1ffd40)
Signed-off-by: Michal Schmidt <mschmidt@redhat.com>
Acked-by: Eilon Greenstein <eilong@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Joe Jin <joe.jin@oracle.com>