clk: ti: make clk_ops const

Make these const as they are only stored in the const field of a
clk_init_data structure.

Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Acked-by: Tero Kristo <t-kristo@ti.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>