drm/amdgpu: Drop redundant pci_enable_pcie_error_reporting()

pci_enable_pcie_error_reporting() enables the device to send ERR_*
Messages.  Since f26e58bf ("PCI/AER: Enable error reporting when AER is
native"), the PCI core does this for all devices during enumeration, so the
driver doesn't need to do it itself.

Remove the redundant pci_enable_pcie_error_reporting() call from the
driver.

Note that this only controls ERR_* Messages from the device.  An ERR_*
Message may cause the Root Port to generate an interrupt, depending on the
AER Root Error Command register managed by the AER service driver.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>