[PATCH net] wireless: mediatek: mt7921: fix Wformat build warning

ARRAY_SIZE() is of type size_t, so the format specfier should
be %zu instead of %lu.

Fixes this build warning:

../drivers/net/wireless/mediatek/mt76/mt7921/main.c: In function ‘mt7921_get_et_stats’:
../drivers/net/wireless/mediatek/mt76/mt7921/main.c:1024:26: warning: format ‘%lu’ expects argument of type ‘long unsigned int’, but argument 4 has type ‘unsigned int’ [-Wformat=]
   dev_err(dev->mt76.dev, "ei: %d  SSTATS_LEN: %lu",

Signed-off-by: Randy Dunlap <redacted>
Cc: Sean Wang <sean.wang@mediatek.com>
Cc: linux-wireless@vger.kernel.org
Cc: Felix Fietkau <nbd@nbd.name>
Cc: Lorenzo Bianconi <redacted>
Cc: Ryder Lee <ryder.lee@mediatek.com>
Cc: Kalle Valo <redacted>
---
 drivers/net/wireless/mediatek/mt76/mt7921/main.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- linux-next-20211022.orig/drivers/net/wireless/mediatek/mt76/mt7921/main.c
+++ linux-next-20211022/drivers/net/wireless/mediatek/mt76/mt7921/main.c

@@ -1021,7 +1021,7 @@ void mt7921_get_et_stats(struct ieee8021
 
 	ei += wi.worker_stat_count;
 	if (ei != ARRAY_SIZE(mt7921_gstrings_stats))
-		dev_err(dev->mt76.dev, "ei: %d  SSTATS_LEN: %lu",
+		dev_err(dev->mt76.dev, "ei: %d  SSTATS_LEN: %zu",
 			ei, ARRAY_SIZE(mt7921_gstrings_stats));
 }