ASoC: Fix build error in sound/soc/omap/n810.c

ASoC: Fix build error in sound/soc/omap/n810.c

Fix below build error which is introduced by
commit 022658 "ASoC: core: Add support for DAI and machine kcontrols".

  CC [M]  sound/soc/omap/n810.o
sound/soc/omap/n810.c: In function 'n810_set_input':
sound/soc/omap/n810.c:194: error: 'codec' undeclared (first use in this function)
sound/soc/omap/n810.c:194: error: (Each undeclared identifier is reported only once
sound/soc/omap/n810.c:194: error: for each function it appears in.)
sound/soc/omap/n810.c:188: warning: unused variable 'card'
make[3]: *** [sound/soc/omap/n810.o] Error 1
make[2]: *** [sound/soc/omap] Error 2
make[1]: *** [sound/soc] Error 2
make: *** [sound] Error 2

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Acked-by: Jarkko Nikula <jarkko.nikula@bitmer.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>