mt76: fix enum type mismatch

There is no 'NONE' version of 'enum mcu_cipher_type', and returning
'MT_CIPHER_NONE' causes a warning:

drivers/net/wireless/mediatek/mt76/mt7921/mcu.c: In function 'mt7921_mcu_get_cipher':
drivers/net/wireless/mediatek/mt76/mt7921/mcu.c:114:24: error: implicit conversion from 'enum mt76_cipher_type' to 'enum mcu_cipher_type' [-Werror=enum-conversion]
  114 |                 return MT_CIPHER_NONE;
      |                        ^~~~~~~~~~~~~~

Add the missing MCU_CIPHER_NONE defintion that fits in here with
the same value.

Fixes: c368362c ("mt76: fix iv and CCMP header insertion")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20210721150745.1914829-1-arnd@kernel.org

drivers/net/wireless/mediatek/mt76/mt7915/mcu.c

@@ -111,7 +111,7 @@ mt7915_mcu_get_cipher(int cipher)
 	case WLAN_CIPHER_SUITE_SMS4:
 		return MCU_CIPHER_WAPI;
 	default:
-		return MT_CIPHER_NONE;
+		return MCU_CIPHER_NONE;
 	}
 }
 

drivers/net/wireless/mediatek/mt76/mt7915/mcu.h

@@ -1073,7 +1073,8 @@ enum {
 };
 
 enum mcu_cipher_type {
-	MCU_CIPHER_WEP40 = 1,
+	MCU_CIPHER_NONE = 0,
+	MCU_CIPHER_WEP40,
 	MCU_CIPHER_WEP104,
 	MCU_CIPHER_WEP128,
 	MCU_CIPHER_TKIP,

drivers/net/wireless/mediatek/mt76/mt7921/mcu.c

@@ -111,7 +111,7 @@ mt7921_mcu_get_cipher(int cipher)
 	case WLAN_CIPHER_SUITE_SMS4:
 		return MCU_CIPHER_WAPI;
 	default:
-		return MT_CIPHER_NONE;
+		return MCU_CIPHER_NONE;
 	}
 }
 

drivers/net/wireless/mediatek/mt76/mt7921/mcu.h

@@ -199,7 +199,8 @@ struct sta_rec_sec {
 } __packed;
 
 enum mcu_cipher_type {
-	MCU_CIPHER_WEP40 = 1,
+	MCU_CIPHER_NONE = 0,
+	MCU_CIPHER_WEP40,
 	MCU_CIPHER_WEP104,
 	MCU_CIPHER_WEP128,
 	MCU_CIPHER_TKIP,