Revert "i965: Make the miptree clear color setter take a gl_color_union"
This reverts commit 1d94aa19877fb702ffacacde28ad7253cce72c97.
The next patch will make depth miptrees use the clear color setter that
was originally being used for color miptrees. Go back to using the
isl_color_value parameter because it's the same type as the
fast_clear_color field used by color and depth miptrees.
Reviewed-by: Topi Pohjolainen <email@example.com>
Reviewed-by: Jason Ekstrand <firstname.lastname@example.org>