PCI: mvebu: Fix potential issue in range parsing

The second parameter of of_read_number() is not the index, but a size.  As
it happens, in this case it may work just fine because of the conversion to
u32 and the favorable endianness on this architecture.

Fixes: 11be6547 ("PCI: mvebu: Adapt to the new device tree layout")
Tested-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Jean-Jacques Hiblot <jjhiblot@traphandler.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Acked-by: Jason Cooper <jason@lakedaemon.net>
Cc: stable@vger.kernel.org	# v3.12+