docs/acpi/erst: add device id for ACPI ERST device in pci-ids.txt

Adding device ID for ERST device in pci-ids.txt. It was missed when ERST
related patches were reviewed.

CC: Eric DeVolder <eric.devolder@oracle.com>
Reviewed-by: Eric DeVolder <eric.devolder@oracle.com>
Signed-off-by: Ani Sinha <ani@anisinha.ca>
Message-Id: <20220223143322.927136-4-ani@anisinha.ca>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

docs/specs/pci-ids.txt

@@ -65,6 +65,7 @@ PCI devices (other than virtio):
 1b36:000f  mdpy (mdev sample device), linux/samples/vfio-mdev/mdpy.c
 1b36:0010  PCIe NVMe device (-device nvme)
 1b36:0011  PCI PVPanic device (-device pvpanic-pci)
+1b36:0012  PCI ACPI ERST device (-device acpi-erst)
 
 All these devices are documented in docs/specs.