intel: Drop program size pointer from vec4/fs assembly getters.

intel: Drop program size pointer from vec4/fs assembly getters.

These days, we're just passing a pointer to a prog_data field, which
we already have access to.  We can just use it directly.

(In the past, it was a pointer to a separate value.)

Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>