i965: Update the indirect buffer in set_clear_color

i965: Update the indirect buffer in set_clear_color

For depth buffers, we avoid fast-clearing if the aux_state is already
CLEAR. We do the same for color buffers only if the clear color
doesn't change. We require that the clear colors match because, in
that case, we don't update the indirect clear color outside of BLORP.

Update the indirect clear color for color buffers as well. We'll
enable the same depth buffer optimization for color buffers in a
later patch.

Note that we're now actually updating the indirect clear color twice
in the case where we use BLORP to perform the fast-clear. This is
only temporary. In later patches, we'll prevent BLORP from performing
the update.

v2: Add more context to the commit message (Topi).

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Topi Pohjolainen <topi.pohjolainen@intel.com>