clk: basic: improve parent_names & return errors

This patch is the basic clk version of 'clk: core: copy parent_names &
return error codes'.

The registration functions are changed to allow the core code to copy
the array of strings and allow platforms to declare those arrays as
__initdata.

This patch also converts all of the basic clk registration functions to
return error codes which better aligns them with the existing clk.h api.

Signed-off-by: Mike Turquette <mturquette@linaro.org>