clk: renesas: Zero init clk_init_data

As clk_core_populate_parent_map() checks clk_init_data.num_parents
first, and checks clk_init_data.parent_names[] before
clk_init_data.parent_data[] and clk_init_data.parent_hws[], leaving the
latter uninitialized doesn't do harm for now.  However, it is better to
play it safe, and initialize all clk_init_data structures to zeroes, to
avoid any current and future members containing uninitialized data.

Remove a few explicit zero initializers, which are now superfluous.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Stephen Boyd <sboyd@kernel.org>
Link: https://lore.kernel.org/r/20210326105434.1574796-1-geert+renesas@glider.be