wifi: brcmsmac: replace deprecated strncpy with memcpy

Let's move away from using strncpy and instead use the more obvious
interface for this context.

For wlc->pub->srom_ccode, we're just copying two bytes from ccode into
wlc->pub->srom_ccode with no expectation that srom_ccode be
NUL-terminated:
wlc->pub->srom_ccode is only used in regulatory_hint():
1193 |       if (wl->pub->srom_ccode[0] &&
1194 |           regulatory_hint(wl->wiphy, wl->pub->srom_ccode))
1195 |               wiphy_err(wl->wiphy, "%s: regulatory hint failed\n", __func__);

We can see that only index 0 and index 1 are accessed.
3307 |       int regulatory_hint(struct wiphy *wiphy, const char *alpha2)
3308 |       {
...  |          ...
3322 |          request->alpha2[0] = alpha2[0];
3323 |          request->alpha2[1] = alpha2[1];
...  |          ...
3332 |       }

Since this is just a simple byte copy with correct lengths, let's use
memcpy(). There should be no functional change.

In a similar boat, both wlc->country_default and
wlc->autocountry_default are just simple byte copies so let's use
memcpy. However, FWICT they aren't used anywhere. (they should be
used or removed -- not in scope of my patch, though).
Signed-off-by: Justin Stitt <justinstitt@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20231017-strncpy-drivers-net-wireless-broadcom-brcm80211-brcmfmac-cfg80211-c-v3-2-af780d74ae38@google.com

drivers/net/wireless/broadcom/brcm80211/brcmsmac/channel.c

@@ -341,7 +341,7 @@ struct brcms_cm_info *brcms_c_channel_mgr_attach(struct brcms_c_info *wlc)
 	/* store the country code for passing up as a regulatory hint */
 	wlc_cm->world_regd = brcms_world_regd(ccode, ccode_len);
 	if (brcms_c_country_valid(ccode))
-		strncpy(wlc->pub->srom_ccode, ccode, ccode_len);
+		memcpy(wlc->pub->srom_ccode, ccode, ccode_len);
 
 	/*
 	 * If no custom world domain is found in the SROM, use the
@@ -354,10 +354,10 @@ struct brcms_cm_info *brcms_c_channel_mgr_attach(struct brcms_c_info *wlc)
 	}
 
 	/* save default country for exiting 11d regulatory mode */
-	strncpy(wlc->country_default, ccode, ccode_len);
+	memcpy(wlc->country_default, ccode, ccode_len);
 
 	/* initialize autocountry_default to driver default */
-	strncpy(wlc->autocountry_default, ccode, ccode_len);
+	memcpy(wlc->autocountry_default, ccode, ccode_len);
 
 	brcms_c_set_country(wlc_cm, wlc_cm->world_regd);