PCI: mvebu: Add help string for CONFIG_PCI_MVEBU option

There is no description for CONFIG_PCI_MVEBU option. Add it.

Link: https://lore.kernel.org/r/20220104153529.31647-6-pali@kernel.org
Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Acked-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

drivers/pci/controller/Kconfig

@@ -10,6 +10,10 @@ config PCI_MVEBU
 	depends on ARM
 	depends on OF
 	select PCI_BRIDGE_EMUL
+	help
+	 Add support for Marvell EBU PCIe controller. This PCIe controller
+	 is used on 32-bit Marvell ARM SoCs: Dove, Kirkwood, Armada 370,
+	 Armada XP, Armada 375, Armada 38x and Armada 39x.
 
 config PCI_AARDVARK
 	tristate "Aardvark PCIe controller"