radeonsi: fix a regression in si_rebind_buffer

Don't update non-buffer images.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=110701


Fixes: 78e35df5 "radeonsi: update buffer descriptors in all contexts after buffer invalidation"

Cc: 19.1 <mesa-stable@lists.freedesktop.org>
Tested-By: Gert Wollny <gert.wollny@collabora..com>
(cherry picked from commit d6053bf2)