cfg80211: fix example REG_RULE usage in Documentation

It's just an example, but lets make it look more real to don't confuse
people about possible REG_RULE usage. Channels are 20 MHz wide, so start
and end frequencies are 10 MHz away from the center one.
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

Documentation/networking/regulatory.txt

@@ -156,12 +156,12 @@ struct ieee80211_regdomain mydriver_jp_regdom = {
 	//.alpha2 =  "99", /* If I have no alpha2 to map it to */
 	.reg_rules = {
 		/* IEEE 802.11b/g, channels 1..14 */
-		REG_RULE(2412-20, 2484+20, 40, 6, 20, 0),
+		REG_RULE(2412-10, 2484+10, 40, 6, 20, 0),
 		/* IEEE 802.11a, channels 34..48 */
-		REG_RULE(5170-20, 5240+20, 40, 6, 20,
+		REG_RULE(5170-10, 5240+10, 40, 6, 20,
 			NL80211_RRF_NO_IR),
 		/* IEEE 802.11a, channels 52..64 */
-		REG_RULE(5260-20, 5320+20, 40, 6, 20,
+		REG_RULE(5260-10, 5320+10, 40, 6, 20,
 			NL80211_RRF_NO_IR|
 			NL80211_RRF_DFS),
 	}