i965: silence incompatible pointer type warning

i965: silence incompatible pointer type warning

src/mesa/drivers/dri/i965/brw_program.c:94:39:
warning: passing argument 1 of ‘_mesa_init_gl_program’ from incompatible
pointer type [-Wincompatible-pointer-types]
          return _mesa_init_gl_program(&prog->program, target, id);

                                       ^

Runtime was unaffected as brw_geometry_program is subclassed from
gl_geometry_program, thus the address passed was the same.

Fixes: bcb56c2c69d (program: convert _mesa_init_gl_program() to take
struct gl_program *)
Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>