ssb: Ignore dangling ethernet cores on wireless devices

Some Broadcom based wireless devices contain dangling ethernet cores.
This triggers the ssb probing mechanism and tries to load the b44 driver
on this core.
Ignore the dangling core in the ssb core scanning code to avoid
access to the core and failure of b44 probing.

Signed-off-by: Michael Buesch <mb@bu3sch.de>
Tested-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>