clk: palmas: constify clk_ops structure

The clk_ops structure is only stored in the ops field of clk_init_data
structures.  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: Stephen Boyd <sboyd@kernel.org>