ASoC: samsung: i2s: Remove virtual device for secondary DAI

For some unknown (maybe historical?) reasons support for secondary I2S DAI
was implemented by adding additional virtual platform device, which was
then probed again with the main I2S driver. This pattern is really hard
to follow and provides no benefits, so lets remove this hack and register
both DAIs during linear probe of Exynos I2S controller driver.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Mark Brown <broonie@kernel.org>