ASoC: s6000-i2s: Fix s6000_i2s_remove() return type

The platform_driver remove callback return type is int not void.

Fixes the following warning:
	sound/soc/s6000/s6000-i2s.c:604:19: warning: incorrect type in initializer (different base types)
	sound/soc/s6000/s6000-i2s.c:604:19:    expected int ( *remove )( ... )
	sound/soc/s6000/s6000-i2s.c:604:19:    got void ( static [toplevel] *<noident>)( ... )

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@linaro.org>