PCI: aardvark: Replace custom macros by standard linux/pci_regs.h macros

PCI: aardvark: Replace custom macros by standard linux/pci_regs.h macros

PCI-E capability macros are already defined in linux/pci_regs.h.
Remove their reimplementation in pcie-aardvark.

Link: https://lore.kernel.org/r/20200430080625.26070-9-pali@kernel.org
Tested-by: Tomasz Maciej Nowak <tmn505@gmail.com>
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>