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[].
Therefore the clk_init_data structure needs to be explicitly initialised
to prevent an unexpected crash if clk_init_data.parent_names[] is a
random value.