maxwell_to_vk: Add R16_SINT

This was somehow missed when the format was added to GL

src/video_core/renderer_vulkan/maxwell_to_vk.cpp

@@ -159,7 +159,7 @@ struct FormatTuple {
     {VK_FORMAT_R16_UNORM, Attachable | Storage},               // R16_UNORM
     {VK_FORMAT_R16_SNORM, Attachable | Storage},               // R16_SNORM
     {VK_FORMAT_R16_UINT, Attachable | Storage},                // R16_UINT
-    {VK_FORMAT_UNDEFINED},                                     // R16_SINT
+    {VK_FORMAT_R16_SINT, Attachable | Storage},                // R16_SINT
     {VK_FORMAT_R16G16_UNORM, Attachable | Storage},            // R16G16_UNORM
     {VK_FORMAT_R16G16_SFLOAT, Attachable | Storage},           // R16G16_FLOAT
     {VK_FORMAT_R16G16_UINT, Attachable | Storage},             // R16G16_UINT