Fixed build.

src/renderer_mtl.h

@@ -877,9 +877,9 @@ namespace bgfx { namespace mtl
 			: m_vshConstantBuffer(NULL)
 			, m_fshConstantBuffer(NULL)
 			, m_vshConstantBufferSize(0)
-			, m_vshConstantBufferAlignmentMask(0)
+			, m_vshConstantBufferAlignment(0)
 			, m_fshConstantBufferSize(0)
-			, m_fshConstantBufferAlignmentMask(0)
+			, m_fshConstantBufferAlignment(0)
 			, m_numPredefined(0)
 			, m_rps(NULL)
 			, m_cps(NULL)