zink: only warn once for SRGB fb without KHR_swapchain_mutable_format
Fixes: 4bb45bcd ("zink: add error logging for SRGB framebuffer without KHR_swapchain_mutable_format")
Fixes: 4bb45bcd ("zink: add error logging for SRGB framebuffer without KHR_swapchain_mutable_format")