Some a4xx firmware doesn't implement the "PFD" (prefetch-disabled)
version of the CP_INDIRECT_BUFFER packet.  So allow for PFD vs PFE per
generation.  Switch a3xx and a4xx over to using prefetch-enabled version
(which is also what blob does.. it seems only on a2xx we cannot use
PFE).

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