RADV Promotes VK_EXT_host_image_copy To Enabled By Default For RDNA1 GPUs

Going back to July 2025 the open-source Radeon RADV Vulkan driver has offered experimental host image copy support with the API's VK_EXT_host_image_copy extension. This has been for RDNA1 and newer GPUs while now GFX10 RDNA 1 GPUs have this extension enabled by default while also enabling experimental support for prior GFX9 era GPUs too. Wei Zhao authored the change to provide experimental VK_EXT_host_image_copy support for GFX9 GPUs using the existing environment variable option. In that same merge request, enabling HIC by default for GFX10 GPUs. This comes with Navi 1x regressions since being addressed. Up to now the VK_EXT_host_image_copy was only enabled by default for GFX10.3 (RDNA2) and newer AMD Radeon graphics. That default enabling for RDNA2 and newer happened earlier this year. VK_EXT_host_image_copy allows for copying data directly between host memory and Vulkan images that can lead to reduced overhead and especially beneficial for iGPUs. This merge added the GFX9 support and GFX10/RDNA1 enabling for host image copy and will be part of Mesa 27.0.