mt76: mt76x0e: make array mt76x0_chan_map static const, makes object smaller

Don't populate the array mt76x0_chan_map on the stack but instead make it
static const. Makes the object code smaller by 80 bytes.

Before:
   text	   data	    bss	    dec	    hex	filename
   7685	   1192	      0	   8877	   22ad	mediatek/mt76/mt76x0/eeprom.o

After:
   text	   data	    bss	    dec	    hex	filename
   7541	   1256	      0	   8797	   225d	mediatek/mt76/mt76x0/eeprom.o

(gcc version 9.2.1, amd64)
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>

drivers/net/wireless/mediatek/mt76/mt76x0/eeprom.c

@@ -212,7 +212,7 @@ void mt76x0_get_tx_power_per_rate(struct mt76x02_dev *dev,
 void mt76x0_get_power_info(struct mt76x02_dev *dev,
 			   struct ieee80211_channel *chan, s8 *tp)
 {
-	struct mt76x0_chan_map {
+	static const struct mt76x0_chan_map {
 		u8 chan;
 		u8 offset;
 	} chan_map[] = {