net/mac8390: Fix log messages

Use dev_foo() to log the slot number instead of the unexpanded "eth%d"
format string.
Disambiguate the two identical "Card type %s is unsupported" messages.

Tested-by: Stan Johnson <userm57@yahoo.com>
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>