clk: Add CLK_HW_INIT_* macros using .parent_hws

With the new clk parenting code, struct clk_init_data was expanded to
include .parent_hws, for clk drivers to directly list parents by
pointing to their respective struct clk_hw's.

Add macros that can take either one single struct clk_hw *, or an array
of them, for drivers to use.

A special CLK_HW_INIT_HWS macro is included, which takes an array of
struct clk_hw *, but sets .num_parents to 1. This variant is to allow
the reuse of the array, instead of having a compound literal allocated
for each clk sharing the same parent.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>