lib/crypto: aes: Drop 'volatile' from aes_sbox and aes_inv_sbox

The volatile keyword is no longer necessary or useful on aes_sbox and
aes_inv_sbox, since the table prefetching is now done using a helper
function that casts to volatile itself and also includes an optimization
barrier.  Since it prevents some compiler optimizations, remove it.

Acked-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20260112192035.10427-36-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>

Author: Eric Biggers

lib/crypto/aes.c

@@ -11,11 +11,7 @@
 #include <linux/module.h>
 #include <linux/unaligned.h>
 
-/*
- * Emit the sbox as volatile const to prevent the compiler from doing
- * constant folding on sbox references involving fixed indexes.
- */
-static volatile const u8 ____cacheline_aligned aes_sbox[] = {
+static const u8 ____cacheline_aligned aes_sbox[] = {
 	0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5,
 	0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76,
 	0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0,
@@ -50,7 +46,7 @@ static volatile const u8 ____cacheline_aligned aes_sbox[] = {
 	0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16,
 };
 
-static volatile const u8 ____cacheline_aligned aes_inv_sbox[] = {
+static const u8 ____cacheline_aligned aes_inv_sbox[] = {
 	0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38,
 	0xbf, 0x40, 0xa3, 0x9e, 0x81, 0xf3, 0xd7, 0xfb,
 	0x7c, 0xe3, 0x39, 0x82, 0x9b, 0x2f, 0xff, 0x87,
@@ -430,7 +426,7 @@ static void __maybe_unused aes_decrypt_generic(const u32 inv_rndkeys[],
 		w[3] = w3;
 	} while (--n);
 
-	aes_prefetch((const void *)aes_inv_sbox, sizeof(aes_inv_sbox));
+	aes_prefetch(aes_inv_sbox, sizeof(aes_inv_sbox));
 	put_unaligned_le32(declast_quarterround(w, 0, *rkp++), &out[0]);
 	put_unaligned_le32(declast_quarterround(w, 1, *rkp++), &out[4]);
 	put_unaligned_le32(declast_quarterround(w, 2, *rkp++), &out[8]);