phy: Remove SOC_EXYNOS4212 dep. from PHY_EXYNOS4X12_USB

Exynos4212 support was removed by commit bca9085e ("ARM: dts:
exynos: remove Exynos4212 support (dead code)").

Remove the SOC_EXYNOS4212 dependency from PHY_EXYNOS4X12_USB.

Discovered with the
https://github.com/ulfalizer/Kconfiglib/blob/master/examples/list_undefined.py


script.

Signed-off-by: Ulf Magnusson <ulfalizer@gmail.com>
Acked-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>