PCI: dwc: dra7xx: Use devm_ioremap_resource() instead of devm_ioremap()

Replace the use of devm_ioremap() with devm_ioremap_resource() as
reported and discussed in the mailing list thread provided.

Link: https://lkml.kernel.org/r/20180120001645.GA21343@lenoch
Signed-off-by: Gustavo Pimentel <gustavo.pimentel@synopsys.com>
[lorenzo.pieralisi@arm.com: updated commit log]
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: Kishon Vijay Abraham I <kishon@ti.com>