ASoC: Change spitz_ext_control to take dapm as argument.

This fixes below build warning:
  CC      sound/soc/pxa/spitz.o
sound/soc/pxa/spitz.c: In function 'spitz_startup':
sound/soc/pxa/spitz.c:116: warning: passing argument 1 of 'spitz_ext_control' from incompatible pointer type
sound/soc/pxa/spitz.c:47: note: expected 'struct snd_soc_card *' but argument is of type 'struct snd_soc_codec *'

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Acked-by: Liam Girdwood <lrg@ti.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>