Remove VK_IMAGE_CREATE_MUTABLE_FORMAT_BIT bit from image creation. (g…

…oogle#543)

No sample mismatch the image format and imageview format, meaning this
feature is not used. In addition, specifying this bit prevents the
driver to make some assumptions, and this can degrade performances

src/ppx/grfx/vk/vk_image.cpp

@@ -35,7 +35,7 @@ Result Image::CreateApiObjects(const grfx::ImageCreateInfo* pCreateInfo)
             extent.height     = pCreateInfo->height;
             extent.depth      = pCreateInfo->depth;
 
-            VkImageCreateFlags createFlags = VK_IMAGE_CREATE_MUTABLE_FORMAT_BIT;
+            VkImageCreateFlags createFlags = 0;
             if (pCreateInfo->type == grfx::IMAGE_TYPE_CUBE) {
                 createFlags |= VK_IMAGE_CREATE_CUBE_COMPATIBLE_BIT;
             }