freedreno: drop needs_rb_fbd

freedreno: drop needs_rb_fbd

We need to emit RB_FRAME_BUFFER_DIMENSION once per batch.. tracking this
in fd_context is wrong when the gmem code executes asynchronously from
the flush_queue worker.  But in fact we don't really need to track it at
all.  We cannot assume previous value at the beginning of the batch
(because of other processes potentially using the GPU), so just drop the
tracking and emit it in _tile_init().

Signed-off-by: Rob Clark <robdclark@gmail.com>