ASoC: samsung: Remove unselectable smdk_wm8580pcm

The SND_SOC_SMDK_WM8580_PCM Kconfig entry depends on either MACH_SMDKV210
or MACH_SMDKC110. Both of which were removed in commit 28c8331d ("ARM:
S5PV210: Remove support for board files") over two years ago. The driver
has been unselectable ever since.

Considering the lack of complaints about this it can be concluded that the
driver is unused and can be removed.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
Reviewed-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Mark Brown <broonie@kernel.org>