freedreno: fix PIPE_TRANSFER_DISCARD_WHOLE_RESOURCE

freedreno: fix PIPE_TRANSFER_DISCARD_WHOLE_RESOURCE

fd_bo_cpu_prep() doesn't realize the bo is already referenced in
unflushed cmdstream.  It could be made to do so (but would have to be
implemented twice, ie. both for msm and kgsl).  But we still can't do
the expected thing if the caller isn't using _NOSYNC.  Because of the
way the tiling works, we need to build quite a bit of cmdstream at flush
time, which is not possible to do at the libdrm level.

So rather than trying to make fd_bo_cpu_prep() smarter than it can
possibly be, just *always* discard and reallocate if the
PIPE_TRANSFER_DISCARD_WHOLE_RESOURCE flag is set.

Signed-off-by: Rob Clark <robclark@freedesktop.org>