mac80211: Fix build error when CONFIG_PM is not defined

When mac80211 is built without CONFIG_PM being defined, the following errors
are output:

net/mac80211/main.c: In function ‘ieee80211_register_hw’:
net/mac80211/main.c:700: error: ‘const struct ieee80211_ops’ has no member named ‘suspend’
net/mac80211/main.c:700: error: ‘const struct ieee80211_ops’ has no member named ‘resume’
make[2]: *** [net/mac80211/main.o] Error 1
make[1]: *** [net/mac80211] Error 2
make[1]: *** Waiting for unfinished jobs....
make: *** [net] Error 2

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>