Fix typo in comment

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/library/aesni.c b/library/aesni.c
index e6143ee..e24527c 100644
--- a/library/aesni.c
+++ b/library/aesni.c
@@ -130,7 +130,7 @@
     ff = _mm_srli_si128(ff, 8);                      // 0:e1+f1
     ee = _mm_slli_si128(ee, 8);                      // e0+f0:0
     *dd = _mm_xor_si128(*dd, ff);                    // d1:d0+e1+f1
-    *cc = _mm_xor_si128(*cc, ee);                    // c1+e0+f1:c0
+    *cc = _mm_xor_si128(*cc, ee);                    // c1+e0+f0:c0
 }
 
 static void gcm_shift(__m128i *cc, __m128i *dd)