phy: exynos-mipi-video: Rewrite handling of phy registers

Controlling Exynos MIPI DPHY is done by handling 2 registers: one for
phy reset and one for enabling it. This patch moves definitions of those
2 registers to speparate exynos_mipi_phy_desc structure, which can be
defined separately for each PHY for each supported hardware variant.
This code rewrite is needed to add support for newer Exynos SoCs, which
have MIPI PHY related registers at different offsets or even different
register regions.

Acked-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>