mt76: make mt76_sar_capa static

Fix the following sparse warning:
drivers/net/wireless/mediatek/mt76/mac80211.c:183:32:
	warning: symbol 'mt76_sar_capa' was not declared. Should it be static?
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Felix Fietkau <nbd@nbd.name>

drivers/net/wireless/mediatek/mt76/mac80211.c

@@ -180,7 +180,7 @@ static const struct cfg80211_sar_freq_ranges mt76_sar_freq_ranges[] = {
 	{ .start_freq = 5725, .end_freq = 5950, },
 };
 
-const struct cfg80211_sar_capa mt76_sar_capa = {
+static const struct cfg80211_sar_capa mt76_sar_capa = {
 	.type = NL80211_SAR_TYPE_POWER,
 	.num_freq_ranges = ARRAY_SIZE(mt76_sar_freq_ranges),
 	.freq_ranges = &mt76_sar_freq_ranges[0],