aer: fix wrong check on expose aer tlp prefix log

when specify TLP Prefix log as using pcie_aer_inject_error,
the TLP prefix log is always discarded. because the check
is incorrect, the End-End TLP Prefix Supported bit
(PCI_EXP_DEVCAP2_EETLPP) should be in Device Capabilities 2 Register.

Signed-off-by: Chen Fan <chen.fan.fnst@cn.fujitsu.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
