ASoC: samsung: i2s: Restore support for the secondary PCM

This patch introduces again registration of additional platform device as
we still need it for registering the secondary dmaengine PCM component.

This patch in most part is a revert of changes done in commit
be2c92eb

 ("ASoC: samsung: i2s: Remove virtual device for secondary DAI")

Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Acked-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Mark Brown <broonie@kernel.org>