iris: Defer uploading sampler state tables until draw time

iris: Defer uploading sampler state tables until draw time

Gallium might call us multiple times to bind subsets of the samplers,
at which point we'd recreate the table a bunch of times.  It doesn't
really buy us anything to do it here - even if we defer to draw time,
the dirty tracking ensures we'll only do it on the first draw after a
bind_sampler_states() call.

We now use the number of samplers specified by the shader instead of
the binding count.  If this number changes, we flag sampler state as
dirty so we re-upload a table with the right number of entries.

This also fixes a bug where ice->state.need_border_colors was never
unset, so once something needed border colors, the pool would always
be pinned in all future batches.

v2: Explicitly flag sampler states as dirty, rather than assuming that
    bind_sampler_states() will be called if the program texture count
    changes.  While this may be true for st/mesa, it isn't the case for
    Gallium HUD.

Tested-by: Timur Kristóf <timur.kristof@gmail.com>
Tested-by: Andre Heider <a.heider@gmail.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>