x86/sev: Use kfree_sensitive() when freeing a SNP message descriptor

Use the proper helper instead of an open-coded variant.

Closes: https://lore.kernel.org/r/202512202235.WHPQkLZu-lkp@intel.com
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Julia Lawall <julia.lawall@inria.fr>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://patch.msgid.link/20260112114147.GBaWTd-8HSy_Xp4S3X@fat_crate.local

Author: bp3tk0v

arch/x86/coco/sev/core.c

@@ -1632,8 +1632,7 @@ void snp_msg_free(struct snp_msg_desc *mdesc)
 	free_shared_pages(mdesc->request, sizeof(struct snp_guest_msg));
 	iounmap((__force void __iomem *)mdesc->secrets);
 
-	memset(mdesc, 0, sizeof(*mdesc));
-	kfree(mdesc);
+	kfree_sensitive(mdesc);
 }
 EXPORT_SYMBOL_GPL(snp_msg_free);