gallium/aux: add PIPE_CAP_MAX_VARYINGS to u_screen
Allows drivers using u_pipe_screen_get_param_defaults
to use a
fallback value for the new pipe cap. Default value of 32 based on what's
used in llvmpipe
Allows drivers using u_pipe_screen_get_param_defaults
to use a
fallback value for the new pipe cap. Default value of 32 based on what's
used in llvmpipe