wifi: brcmfmac: Replace one-element array with flexible-array member

One-element arrays are deprecated, and we are replacing them with flexible
array members instead. So, replace one-element array with flexible-array
member in struct brcmf_tlv.

This helps with the ongoing efforts to tighten the FORTIFY_SOURCE
routines on memcpy() and help us make progress towards globally
enabling -fstrict-flex-arrays=3 [1].

This results in no differences in binary output.

Link: https://github.com/KSPP/linux/issues/79
Link: https://github.com/KSPP/linux/issues/253
Link: https://gcc.gnu.org/pipermail/gcc-patches/2022-October/602902.html [1]
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/Y9xjizhMujNEtpB4@work

drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.h

@@ -383,7 +383,7 @@ struct brcmf_cfg80211_info {
 struct brcmf_tlv {
 	u8 id;
 	u8 len;
-	u8 data[1];
+	u8 data[];
 };
 
 static inline struct wiphy *cfg_to_wiphy(struct brcmf_cfg80211_info *cfg)