ASoC: samsung: no more support for S5P6440 and S5P6450 SoCs

This patch removes s5p64x0 related WM8580 because of removing support
for s5p64x0 SoCs.

Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>
[pebolle@tiscali.nl: reported missing dependency for smdk6450]
Reported-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Mark Brown <broonie@linaro.org>