net/sonic: Clean up and modernize log messages

net/sonic: Clean up and modernize log messages

Add missing printk severity levels by adopting pr_foo() calls for the
platform_driver and dev_foo() calls for the nubus_driver.
Avoid KERN_CONT usage as per advice from checkpatch.
Avoid #ifdef around printk calls.
Don't log driver probe messages after calling register_netdev().

Cc: Thomas Bogendoerfer <[email protected]>
Cc: Chris Zankel <[email protected]>
Tested-by: Stan Johnson <[email protected]>
Signed-off-by: Finn Thain <[email protected]>
Signed-off-by: David S. Miller <[email protected]>