ACPI/IORT: Remove the unused __get_pci_rid()

Since commit bc8648d4 ("ACPI/IORT: Handle PCI aliases properly for
IOMMUs"), __get_pci_rid() has become actually unused and can be removed.

Signed-off-by: Zenghui Yu <yuzenghui@huawei.com>
Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: Hanjun Guo <guohanjun@huawei.com>
Link: https://lore.kernel.org/r/20200509093430.1983-1-yuzenghui@huawei.com


Signed-off-by: Will Deacon <will@kernel.org>