smc91x: fix unused flags warnings on UP systems

Local flags variables will be declared whenever these functions get used,
but obviously on UP systems the flags parameter won't be touched.  So add
some dummy ops that get optimized away anyways to satisfy gcc's warnings.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Acked-by: Nicolas Pitre <nico@fluxnic.net>
Signed-off-by: David S. Miller <davem@davemloft.net>