anv/blorp: Ignore clears for attachments first used as resolve destinations

anv/blorp: Ignore clears for attachments first used as resolve destinations

Otherwise, we'll try to clear it the first time it's used as a draw so if
you do some multisampled rendering, resolve to an attachment, and then draw
on top of the single-sampled attachment, we might accidentally clear it.

Cc: "13.0" <mesa-stable@lists.freedesktop.org>
(cherry picked from commit ccdf9af39265ef3478fac4d13b19e9d17fbbcab7)