sun4i_wemac: Do not use MAC from fex if it is 000000000000

Also improve MAC address logging:
-In case it comes from the cmdline, print the actual address after parsing,
 not the string from the kerne cmdline
-Log a message when using a MAC address from the fex file
-The fixed prefix for the MAC-address from the SID is 02 not 00

Signed-off-by: Hans de Goede <hdegoede@redhat.com>