drm/imx: imx-tve: constify clk_ops structure

The clk_ops structure is only stored in the ops field of a
clk_init_data structure.  This field is const, so the clk_ops
structure can be const as well.

Identified and transformed using Coccinelle.

Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>