zink: translate gl_FragColor to gl_FragData before ntv to fix multi-rt output

zink: translate gl_FragColor to gl_FragData before ntv to fix multi-rt output

according to EXT_multiview_draw_buffers, gl_FragColor outputs to all available
render targets when used, so we need to translate this to gl_FragData[PIPE_MAX_COLOR_BUFS]
in order to correctly handle more than one color buffer attachment

this fixes the rest of spec@arb_framebuffer_object tests in piglit

Reviewed-by: Erik Faye-Lund <erik.faye-lund@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5687>