virgl: don't mark buffers as unclean after a write

We can mark the buffer unclean if it's ever bound as a TBO,
SSBO, ABO, or image.

This improves

dEQP-GLES3.performance.buffer.data_upload.function_call.map_buffer_range.new_specified_buffer.flag_write_full.stream_draw

from 9.58 MB/s to 451.17 MB/s.

v2: Track buffer cleanliness as a function of bindings (Ilia).
v3: virgl_modify_clean --> virgl_dirty_res (Erik)

Tested-By: Gert Wollny <gert.wollny@collabora.com>
Reviewed-by: Erik Faye-Lund <erik.faye-lund@collabora.com>
(cherry picked from commit 89b4798c)

With this and previous two patches, the performance of virgl on top of
a r600 (AMD 6870 HD) host improves as follows:

         | FPS avg |  Score
--------------------------------
 before  |   8.2   |   343
 after   |  21.9   |   916

         | FPS avg |  Score
--------------------------------
 before  |  13.2   |   333
 after   |  32.3   |   790