Exynos5440 SoC support has been dropped since commit 8c83315d ("ARM:
dts: exynos: Remove Exynos5440"). Rework this driver to support DWC PCIe
variant found in the Exynos5433 SoCs.

The main difference in Exynos5433 variant is lack of the MSI support
(the MSI interrupt is not even routed to the CPU).

[mszyprow: reworked the driver to support only Exynos5433 variant,
	   simplified code, rebased onto current kernel code, added
	   regulator support, converted to the regular platform driver,
	   removed MSI related code, rewrote commit message, added help]

Link: https://lore.kernel.org/r/20201113170139.29956-6-m.szyprowski@samsung.comSigned-off-by: NJaehoon Chung <jh80.chung@samsung.com>
Signed-off-by: NMarek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: NLorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: NRob Herring <robh@kernel.org>
Acked-by: NKrzysztof Kozlowski <krzk@kernel.org>
Acked-by: NJingoo Han <jingoohan1@gmail.com>