Remove Makefile.release

We now prefer to do local clone instead of make distclean.

Link: https://lore.kernel.org/ltp/[email protected]/T/#u
Reviewed-by: Li Wang <[email protected]>
Reviewed-by: Avinesh Kumar <[email protected]>
Signed-off-by: Petr Vorel <[email protected]>

Author: pevik