crypto/internal/fips140/aes/gcm: use aes.EncryptBlockInternal on ppc64x and s390x

Left them out of CL 636775 because I did a search by reference, which
does not span architectures.

Fixes crypto/cipher.TestFIPSServiceIndicator failure on ppc64x and s390x.

For #69536

Change-Id: I34b49705a7099066e8c3871a7a34b394a9298e98
Reviewed-on: https://go-review.googlesource.com/c/go/+/637175
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Roland Shoemaker <roland@golang.org>
Auto-Submit: Filippo Valsorda <filippo@golang.org>
Reviewed-by: Daniel McCarney <daniel@binaryparadox.net>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

src/crypto/internal/fips140/aes/gcm/gcm_ppc64x.go

@@ -51,7 +51,7 @@ func initGCM(g *GCM) {
 	}
 
 	hle := make([]byte, gcmBlockSize)
-	g.cipher.Encrypt(hle, hle)
+	aes.EncryptBlockInternal(&g.cipher, hle, hle)
 
 	// Reverse the bytes in each 8 byte chunk
 	// Load little endian, store big endian
@@ -133,7 +133,7 @@ func seal(out []byte, g *GCM, nonce, plaintext, data []byte) {
 	var counter, tagMask [gcmBlockSize]byte
 	deriveCounter(&counter, nonce, &g.productTable)
 
-	g.cipher.Encrypt(tagMask[:], counter[:])
+	aes.EncryptBlockInternal(&g.cipher, tagMask[:], counter[:])
 	gcmInc32(&counter)
 
 	counterCrypt(&g.cipher, out, plaintext, &counter)
@@ -151,7 +151,7 @@ func open(out []byte, g *GCM, nonce, ciphertext, data []byte) error {
 	var counter, tagMask [gcmBlockSize]byte
 	deriveCounter(&counter, nonce, &g.productTable)
 
-	g.cipher.Encrypt(tagMask[:], counter[:])
+	aes.EncryptBlockInternal(&g.cipher, tagMask[:], counter[:])
 	gcmInc32(&counter)
 
 	var expectedTag [gcmTagSize]byte

src/crypto/internal/fips140/aes/gcm/gcm_s390x.go

@@ -55,7 +55,7 @@ func initGCM(g *GCM) {
 		return
 	}
 	// Note that hashKey is also used in the KMA codepath to hash large nonces.
-	g.cipher.Encrypt(g.hashKey[:], g.hashKey[:])
+	aes.EncryptBlockInternal(&g.cipher, g.hashKey[:], g.hashKey[:])
 }
 
 // ghashAsm uses the GHASH algorithm to hash data with the given key. The initial
@@ -115,7 +115,7 @@ func counterCrypt(g *GCM, dst, src []byte, cnt *[gcmBlockSize]byte) {
 	}
 	if len(src) > 0 {
 		var x [16]byte
-		g.cipher.Encrypt(x[:], cnt[:])
+		aes.EncryptBlockInternal(&g.cipher, x[:], cnt[:])
 		for i := range src {
 			dst[i] = src[i] ^ x[i]
 		}