Revert "[dxgi] Use VK_FORMAT_A8_UNORM if available"

This reverts commit 6a5ed02.

Native A8 breaks Crysis 2/3 Remastered for unknown reasons.

src/dxgi/dxgi_format.cpp

@@ -318,10 +318,12 @@ namespace dxvk {
       VK_FORMAT_R8_UINT,
       VK_IMAGE_ASPECT_COLOR_BIT },
     // DXGI_FORMAT_A8_UNORM
-    { VK_FORMAT_A8_UNORM_KHR,
+    { VK_FORMAT_R8_UNORM,
       VK_FORMAT_UNDEFINED,
-      VK_FORMAT_R8_UINT,
-      VK_IMAGE_ASPECT_COLOR_BIT, 0 },
+      VK_FORMAT_UNDEFINED,
+      VK_IMAGE_ASPECT_COLOR_BIT, 0,
+      { VK_COMPONENT_SWIZZLE_ZERO, VK_COMPONENT_SWIZZLE_ZERO,
+        VK_COMPONENT_SWIZZLE_ZERO, VK_COMPONENT_SWIZZLE_R }},
     // DXGI_FORMAT_R1_UNORM
     { }, // Unsupported
     // DXGI_FORMAT_R9G9B9E5_SHAREDEXP
@@ -858,16 +860,6 @@ namespace dxvk {
       RemapDepthFormat(DXGI_FORMAT_X24_TYPELESS_G8_UINT,  VK_FORMAT_D32_SFLOAT_S8_UINT);
       RemapDepthFormat(DXGI_FORMAT_D24_UNORM_S8_UINT,     VK_FORMAT_D32_SFLOAT_S8_UINT);
     }
-
-    // Map A8_UNORM to R8_UNORM with appropriate swizzles if necessary
-    if (!CheckImageFormatSupport(device, VK_FORMAT_A8_UNORM_KHR,
-          VK_FORMAT_FEATURE_2_SAMPLED_IMAGE_BIT |
-          VK_FORMAT_FEATURE_2_COLOR_ATTACHMENT_BIT |
-          VK_FORMAT_FEATURE_2_STORAGE_IMAGE_BIT)) {
-      RemapColorFormat(DXGI_FORMAT_A8_UNORM, VK_FORMAT_R8_UNORM,
-        { VK_COMPONENT_SWIZZLE_ZERO, VK_COMPONENT_SWIZZLE_ZERO,
-          VK_COMPONENT_SWIZZLE_ZERO, VK_COMPONENT_SWIZZLE_R });
-    }
   }