ACPI/IORT: Stub out ACS functions when CONFIG_PCI is not set

Remove PCI dependent code out of iort.c when CONFIG_PCI is not defined.
A quick search reveals the following functions:
1. pci_request_acs()
2. pci_domain_nr()
3. pci_is_root_bus()
4. to_pci_dev()

Both pci_domain_nr() and pci_is_root_bus() are defined in linux/pci.h.
pci_domain_nr() is a stub function when CONFIG_PCI is not set and
pci_is_root_bus() just returns a reference to a structure member which
is still valid without CONFIG_PCI set.

to_pci_dev() is a macro that expands to container_of.

pci_request_acs() is the only code that gets pulled in from drivers/pci/*.c

Signed-off-by: Sinan Kaya <okaya@kernel.org>
Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>