treewide: Replace zero-length arrays with flexible-array members

There is a regular need in the kernel to provide a way to declare
having a dynamically sized set of trailing elements in a structure.
Kernel code should always use “flexible array members”[1] for these
cases. The older style of one-element or zero-length arrays should
no longer be used[2].

This code was transformed with the help of Coccinelle:
(next-20220214$ spatch --jobs $(getconf _NPROCESSORS_ONLN) --sp-file script.cocci --include-headers --dir . > output.patch)

@@
identifier S, member, array;
type T1, T2;
@@

struct S {
  ...
  T1 member;
  T2 array[
- 0
  ];
};

UAPI and wireless changes were intentionally excluded from this patch
and will be sent out separately.

[1] https://en.wikipedia.org/wiki/Flexible_array_member
[2] https://www.kernel.org/doc/html/v5.16/process/deprecated.html#zero-length-and-one-element-arrays

Link: https://github.com/KSPP/linux/issues/78
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

arch/x86/include/asm/microcode_intel.h

@@ -19,7 +19,7 @@ struct microcode_header_intel {
 
 struct microcode_intel {
 	struct microcode_header_intel hdr;
-	unsigned int            bits[0];
+	unsigned int            bits[];
 };
 
 /* microcode format is extended from prescott processors */
@@ -33,7 +33,7 @@ struct extended_sigtable {
 	unsigned int            count;
 	unsigned int            cksum;
 	unsigned int            reserved[3];
-	struct extended_signature sigs[0];
+	struct extended_signature sigs[];
 };
 
 #define DEFAULT_UCODE_DATASIZE	(2000)