rtw88: fix subscript above array bounds compiler warning

My compiler complains about:

drivers/net/wireless/realtek/rtw88/phy.c: In function ‘rtw_phy_rf_power_2_rssi’:
drivers/net/wireless/realtek/rtw88/phy.c:430:26: warning: array subscript is above array bounds [-Warray-bounds]
  linear = db_invert_table[i][j];

According to comment power_db should be in range 1 ~ 96 .
To fix add check for boundaries before access the array.
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Acked-by: Yan-Hsuan Chuang <yhchuang@realtek.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/realtek/rtw88/phy.c

@@ -423,6 +423,11 @@ static u64 rtw_phy_db_2_linear(u8 power_db)
 	u8 i, j;
 	u64 linear;
 
+	if (power_db > 96)
+		power_db = 96;
+	else if (power_db < 1)
+		return 1;
+
 	/* 1dB ~ 96dB */
 	i = (power_db - 1) >> 3;
 	j = (power_db - 1) - (i << 3);