radv: rebase radv_entrypoints_gen.py on anv_entrypoints_gen.py

radv: rebase radv_entrypoints_gen.py on anv_entrypoints_gen.py

The two generators forked from each other, and they remain basically the
same. This rebases the radv version on the anv version, but with the
radv changes ported over. The result is that we get rid of the "cat |"
madness and gain mako, correct "generated by" attributions, and write
files out directly.

The only differences between the output is whitespace and comments.

Signed-off-by: Dylan Baker <dylanx.c.baker@intel.com>
Acked-by: Dave Airlie <airlied@redhat.com>