compiling clk-main.c and clk-generated.c results in:

warning: passing argument 1 of 'memcpy' discards 'const' qualifier from
pointer target type [-Wdiscarded-qualifiers]
  memcpy(clkmain->clk.parent_names, parent_names, parents_array_size);
           ~~~~~~~~~~~~^~~~~~~~~~~~~

Avoid this by replacing the xzalloc+memcpy pair with xmemdup.
Zero-initialization of the buffer isn't necessary, because
memcpy spans the whole buffer.

Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>