NFP has a prng register, which we can read to obtain a u32 worth
of pseudo random data.  Generate code for it.
Signed-off-by: NJakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: NQuentin Monnet <quentin.monnet@netronome.com>
Reviewed-by: NJiong Wang <jiong.wang@netronome.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>