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_gscan_config.

Important to mention is that doing a build before/after this patch results
in no binary output differences.

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].

Link: KSPP#79
Link: KSPP#241
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/7694550aa9a2753a73a687f61af9441c8cf52fd7.1668466470.git.gustavoars@kernel.org

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

@@ -1049,7 +1049,7 @@ struct brcmf_gscan_config {
 	u8 count_of_channel_buckets;
 	u8 retry_threshold;
 	__le16  lost_ap_window;
-	struct brcmf_gscan_bucket_config bucket[1];
+	struct brcmf_gscan_bucket_config bucket[];
 };
 
 /**

drivers/net/wireless/broadcom/brcm80211/brcmfmac/pno.c

@@ -405,7 +405,7 @@ static int brcmf_pno_config_sched_scans(struct brcmf_if *ifp)
 	if (n_buckets < 0)
 		return n_buckets;
 
-	gsz = sizeof(*gscan_cfg) + (n_buckets - 1) * sizeof(*buckets);
+	gsz = sizeof(*gscan_cfg) + n_buckets * sizeof(*buckets);
 	gscan_cfg = kzalloc(gsz, GFP_KERNEL);
 	if (!gscan_cfg) {
 		err = -ENOMEM;