anv: narrow flushing of the render target to buffer writes

In commit 9a7b319903 ("anv/query: flush render target before
copying results") we tracked all the render target writes to apply a
flushes in the vkCopyQueryResults(). But we can narrow this down to
only when we write a buffer (which is the only input of
vkCopyQueryResults).

v2: Drop newer render target write flags introduce by 1952fd8d2c
    ("anv: Implement VK_EXT_conditional_rendering for gen 7.5+")

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net> (v1)

src/intel/vulkan/genX_blorp_exec.c

@@ -268,5 +268,4 @@ genX(blorp_exec)(struct blorp_batch *batch,
    cmd_buffer->state.gfx.vb_dirty = ~0;
    cmd_buffer->state.gfx.dirty = ~0;
    cmd_buffer->state.push_constants_dirty = ~0;
-   cmd_buffer->state.pending_pipe_bits |= ANV_PIPE_RENDER_TARGET_WRITES;
 }