ENGR00234501 ASoC: spdif: fix Ubuntu reboot hang issue

ENGR00234501 ASoC: spdif: fix Ubuntu reboot hang issue

  spdif driver registered kcontrol for ALSA subsystem controlling, while some
of those kcontrol functions lack of clk_enable() before register-accessing. So
system would definitely hang when those functions're called, which did happen
during reboot test on Ubuntu due to its pulse-audio.
  This patch added paired clk_en/disable() to those functions so as to pevent
system hang issue.

Acked-by: Wang Shengjiu <b02247@freescale.com>
Tested-by: Anson Huang <b20788@freescale.com>
Signed-off-by: Nicolin Chen <b42378@freescale.com>