gallium: Obtain ARB_framebuffer_no_attachment constants

gallium: Obtain ARB_framebuffer_no_attachment constants

Set default values for the constants required in
ARB_framebuffer_no_attachments and obtained the number
of layers from ``PIPE_CAP_MAX_TEXTURE_ARRAY_LAYERS``.

We also obtain the MaxFramebufferSamples value using
a query back to the driver for PIPE_FORMAT_NONE.

V.1:
 Merge if branch predicates into one branch.
 Move const init into st_init_limits()

[airlied: whitespace fixup]
Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>