iris: Don't skip fast depth clears if the color changed

iris: Don't skip fast depth clears if the color changed

We depend on BLORP to convert the clear color and write it into the
clear color buffer for us.  However, we weren't bothering to call blorp
in the case where the state is ISL_AUX_STATE_CLEAR.  This leads to the
clear color not getting properly updated if we have back-to-back clears
with different clear colors.  Technically, we could go out of our way to
set the clear color directly from iris in this case but this is a case
we're unlikely to see in the wild so let's not bother.  This matches
what we already do for color surfaces.

Cc: mesa-stable@lists.freedesktop.org
Reported-by: Mark Janes <mark.a.janes@intel.com>
Reviewed-by: Nanley Chery <nanley.g.chery@intel.com>
Tested-by: Marge Bot <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4073>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4073>