nvc0: rework nvc0_compute_validate_program()

nvc0: rework nvc0_compute_validate_program()

Reduce the amount of duplicated code by re-using
nvc0_program_validate(). While we are at it, change the prototype
to return void and remove nvc0_compute.h which is now useless.

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Acked-by: Pierre Moreau <pierre.morrow@free.fr>
Acked-by: Ilia Mirkin <imirkin@alum.mit.edu>