dt-bindings: PCI: exynos: drop samsung,exynos5440-pcie binding

Exynos5440 SoC support has been dropped since commit 8c83315d ("ARM:
dts: exynos: Remove Exynos5440"). Drop the obsolete bindings for
exynos5440-pcie.

Link: https://lore.kernel.org/r/20201113170139.29956-2-m.szyprowski@samsung.com


Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
Reviewed-by: Jingoo Han <jingoohan1@gmail.com>