phy: Add driver for Exynos DP PHY

Add a PHY provider driver for the Samsung Exynos SoC Display Port PHY.

Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Reviewed-by: Tomasz Figa <t.figa@samsung.com>
Cc: Sylwester Nawrocki <s.nawrocki@samsung.com>
Acked-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>