Fix ifdef mismatch for mirroruv

source/row_gcc.cc

Index: source/row_gcc.cc
diff --git a/source/row_gcc.cc b/source/row_gcc.cc
index 80b2a95aa1094f8e05c96712a51bf4788d909d80..8ac5084b6d27410f08212c4bbabc8e02ea68f17a 100644
--- a/source/row_gcc.cc
+++ b/source/row_gcc.cc
@@ -2521,7 +2521,7 @@ void MirrorRow_AVX2(const uint8* src, uint8* dst, int width) {
 }
 #endif  // HAS_MIRRORROW_AVX2
 
-#ifdef HAS_MIRRORROW_UV_SSSE3
+#ifdef HAS_MIRRORUVROW_SSSE3
 // Shuffle table for reversing the bytes of UV channels.
 static uvec8 kShuffleMirrorUV = {
   14u, 12u, 10u, 8u, 6u, 4u, 2u, 0u, 15u, 13u, 11u, 9u, 7u, 5u, 3u, 1u
@@ -2552,7 +2552,7 @@ void MirrorUVRow_SSSE3(const uint8* src, uint8* dst_u, uint8* dst_v,
     "xmm0", "xmm1"
   );
 }
-#endif  // HAS_MIRRORROW_UV_SSSE3
+#endif  // HAS_MIRRORUVROW_SSSE3
 
 #ifdef HAS_ARGBMIRRORROW_SSE2