net/ncsi: Don't probe on the reserved channel ID (0x1f)

We needn't send CIS (Clear Initial State) command to the NCSI
reserved channel (0x1f) in the enumeration. We shouldn't receive
a valid response from CIS on NCSI channel 0x1f.

Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: David S. Miller <davem@davemloft.net>