PCI: keystone: Prevent ARM32 specific code to be compiled for ARM64

hook_fault_code() is an ARM32 specific API for hooking into data abort.

AM65X platforms (that integrate ARM v8 cores and select CONFIG_ARM64 as
arch) rely on pci-keystone.c but on them the enumeration of a
non-present BDF does not trigger a bus error, so the fixup exception
provided by calling hook_fault_code() is not needed and can be guarded
with CONFIG_ARM.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
[lorenzo.pieralisi@arm.com: commit log]
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>

drivers/pci/controller/dwc/pci-keystone.c

@@ -710,6 +710,7 @@ static int ks_pcie_config_legacy_irq(struct keystone_pcie *ks_pcie)
 	return ret;
 }
 
+#ifdef CONFIG_ARM
 /*
  * When a PCI device does not exist during config cycles, keystone host gets a
  * bus error instead of returning 0xffffffff. This handler always returns 0
@@ -729,6 +730,7 @@ static int ks_pcie_fault(unsigned long addr, unsigned int fsr,
 
 	return 0;
 }
+#endif
 
 static int __init ks_pcie_init_id(struct keystone_pcie *ks_pcie)
 {
@@ -778,12 +780,14 @@ static int __init ks_pcie_host_init(struct pcie_port *pp)
 	if (ret < 0)
 		return ret;
 
+#ifdef CONFIG_ARM
 	/*
 	 * PCIe access errors that result into OCP errors are caught by ARM as
 	 * "External aborts"
 	 */
 	hook_fault_code(17, ks_pcie_fault, SIGBUS, 0,
 			"Asynchronous external abort");
+#endif
 
 	ks_pcie_start_link(pci);
 	dw_pcie_wait_for_link(pci);