Replace .init_time() hook with of_clk_init() for DT targets.

Based on:
  d4347ee ARM: i.MX27 clk: Use of_clk_init() for DT case
Signed-off-by: Denis Carikli <denis@eukrea.com>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Shawn Guo <shawn.guo@freescale.com>