wireless: Add channel/frequency conversions to ieee80211.h

Added mappings for FHSS, DSSS and OFDM channels - with macros to point
HR DSSS and ERP to the DSSS mappings. Currently just static inline
functions.

Use the new functions in the older fullmac drivers. This eliminates a
number of const static buffers and removes a couple of range checks that
are now redundant.

Signed-off-by: David Kilroy <kilroyd@googlemail.com>
Acked-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Richard Farina <sidhayn@gmail.com>
Acked-by: Jeroen Vreeken <pe1rxq@amsat.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/zd1201.c b/drivers/net/wireless/zd1201.c
index b45c27d..6226ac2 100644
--- a/drivers/net/wireless/zd1201.c
+++ b/drivers/net/wireless/zd1201.c
@@ -919,10 +919,9 @@
 	if (freq->e == 0)
 		channel = freq->m;
 	else {
-		if (freq->m >= 2482)
-			channel = 14;
-		if (freq->m >= 2407)
-			channel = (freq->m-2407)/5;
+		channel = ieee80211_freq_to_dsss_chan(freq->m);
+		if (channel < 0)
+			channel = 0;
 	}
 
 	err = zd1201_setconfig16(zd, ZD1201_RID_CNFOWNCHANNEL, channel);