[HAMRADIO]: driver cleanups

Misc related cleanups in hamradio drivers:

 o Use symbolic constants instead of magic numbers
 o Don't try to handle the case where AX.25 isn't configured - the kernel
   configuration doesn't permit that.
 o Remove useless headers

Signed-off-by: Ralf Baechle DL5RB <ralf@linux-mips.org>
Signed-off-by: David S. Miller <davem@davemloft.net>