drm/radeon/evergreen: make texdw[] array larger

We store stuff in texdw[7] so this array needs to have 8 elements.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Jerome Glisse <jglisse@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>