ath9k: fix spelling mistake: "meaurement" -> "measurement"

Trivial fix to spelling mistake in ath_err message
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>

drivers/net/wireless/ath/ath9k/hw.c

@@ -731,7 +731,7 @@ u32 ar9003_get_pll_sqsum_dvc(struct ath_hw *ah)
 		udelay(100);
 
 		if (WARN_ON_ONCE(i >= 100)) {
-			ath_err(common, "PLL4 meaurement not done\n");
+			ath_err(common, "PLL4 measurement not done\n");
 			break;
 		}