i965/vec4: Eliminate the vec4_generator class altogether.

i965/vec4: Eliminate the vec4_generator class altogether.

We really weren't taking advantage of vec4_generator being a class.
By adding a "p" parameter to the helper methods, and "prog_data" to
ones which need binding table information, we can convert everything
to static functions.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Matt Turner <mattst88@gmail.com>