wifi: mt76: mt7996: Initialize hdr before passing to skb_put_data()

commit 87b07a1 upstream.

A new warning in clang [1] points out a couple of places where a hdr
variable is not initialized then passed along to skb_put_data().

  drivers/net/wireless/mediatek/mt76/mt7996/mcu.c:1894:21: warning: variable 'hdr' is uninitialized when passed as a const pointer argument here [-Wuninitialized-const-pointer]
   1894 |         skb_put_data(skb, &hdr, sizeof(hdr));
        |                            ^~~
  drivers/net/wireless/mediatek/mt76/mt7996/mcu.c:3386:21: warning: variable 'hdr' is uninitialized when passed as a const pointer argument here [-Wuninitialized-const-pointer]
   3386 |         skb_put_data(skb, &hdr, sizeof(hdr));
        |                            ^~~

Zero initialize these headers as done in other places in the driver when
there is nothing stored in the header.

Cc: stable@vger.kernel.org
Fixes: 98686cd ("wifi: mt76: mt7996: add driver for MediaTek Wi-Fi 7 (802.11be) devices")
Link: llvm/llvm-project@00dacf8 [1]
Closes: ClangBuiltLinux/linux#2104
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Link: https://patch.msgid.link/20250715-mt7996-fix-uninit-const-pointer-v1-1-b5d8d11d7b78@kernel.org
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: nathanchance

drivers/net/wireless/mediatek/mt76/mt7996/mcu.c

@@ -1879,8 +1879,8 @@ mt7996_mcu_get_mmps_mode(enum ieee80211_smps_mode smps)
 int mt7996_mcu_set_fixed_rate_ctrl(struct mt7996_dev *dev,
 				   void *data, u16 version)
 {
+	struct uni_header hdr = {};
 	struct ra_fixed_rate *req;
-	struct uni_header hdr;
 	struct sk_buff *skb;
 	struct tlv *tlv;
 	int len;
@@ -3377,7 +3377,7 @@ int mt7996_mcu_set_hdr_trans(struct mt7996_dev *dev, bool hdr_trans)
 {
 	struct {
 		u8 __rsv[4];
-	} __packed hdr;
+	} __packed hdr = {};
 	struct hdr_trans_blacklist *req_blacklist;
 	struct hdr_trans_en *req_en;
 	struct sk_buff *skb;