radv: Add radv_shader_type to fix gs_copy and trap handler handling

radv: Add radv_shader_type to fix gs_copy and trap handler handling

is_gs_copy_shader and is_trap_handler_shader were cleared in
radv_init_shader_args. This restores the original behaviour.

Fixes: 67635bb ("radv: zero-initialize radv_shader_args right before declaring them")
Reviewed-by: Timur Kristóf <timur.kristof@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/22382>