make_surface() contained a giant if-tree for creation of aux surfaces.
Move the if-tree into its own function, add_aux_surface_if_supported().
This will simplify future changes for VK_EXT_image_drm_format_modifier.
This patch merely moves the code verbatim, then extracts duplicate
assertions to the top.
v2: Rename func to add_aux_surface_if_supported [for jekstrand].
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4096>