net/sonic: Replace custom debug logging with netif_* calls

Eliminate duplicated debug code by moving it into the core driver.
Don't log the only valid silicon revision number (it's in the source).

Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Chris Zankel <chris@zankel.net>
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>