radeonsi: fix invalidating bindless buffer descriptors

radeonsi: fix invalidating bindless buffer descriptors

The VA is stored at [4:5], not [0:1]. This invalidated all
texture buffer descriptors when they were made resident in
the current context.

This removes few partial flushes and cache invalidations which
are needed when updating a bindless descriptor on the fly with
a WRITE_DATA packet.

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>