ASoC: buildfix for OSK

Buildfix:

  CC      sound/soc/omap/osk5912.o
  sound/soc/omap/osk5912.c: In function 'osk_soc_init':
  sound/soc/omap/osk5912.c:189: error: implicit declaration of function 'clk_get_usecount'
  make[3]: *** [sound/soc/omap/osk5912.o] Error 1

There's no such (standard) clock interface.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>