PCI: mvebu: Add support for Advanced Error Reporting registers on emulated bridge

AER registers start at mvebu offset 0x0100. Registers PCI_ERR_ROOT_COMMAND,
PCI_ERR_ROOT_STATUS and PCI_ERR_ROOT_ERR_SRC are not supported on pre-XP
hardware and returns zeros.

Note that AER interrupt is not supported yet as mvebu emulated bridge does
not implement interrupts support at all yet.

Also remove custom macro PCIE_HEADER_LOG_4_OFF as it is unused and
correctly this register should be referenced via standard macros with
offset, e.g. as: PCIE_CAP_PCIERR_OFF + PCI_ERR_HEADER_LOG + 4.

Link: https://lore.kernel.org/r/20220222155030.988-8-pali@kernel.org


Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>