arm64: efi: fix initcall return values

Even though initcall return values are typically ignored, the
prototype is to return 0 on success or a negative errno value on
error. So fix the arm_enable_runtime_services() implementation to
return 0 on conditions that are not in fact errors, and return a
meaningful error code otherwise.
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Matt Fleming <matt@codeblueprint.co.uk>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/kernel/efi.c

@@ -280,12 +280,12 @@ static int __init arm64_enable_runtime_services(void)
 
 	if (!efi_enabled(EFI_BOOT)) {
 		pr_info("EFI services will not be available.\n");
-		return -1;
+		return 0;
 	}
 
 	if (efi_runtime_disabled()) {
 		pr_info("EFI runtime services will be disabled.\n");
-		return -1;
+		return 0;
 	}
 
 	pr_info("Remapping and enabling EFI services.\n");
@@ -295,7 +295,7 @@ static int __init arm64_enable_runtime_services(void)
 						   mapsize);
 	if (!memmap.map) {
 		pr_err("Failed to remap EFI memory map\n");
-		return -1;
+		return -ENOMEM;
 	}
 	memmap.map_end = memmap.map + mapsize;
 	efi.memmap = &memmap;
@@ -304,13 +304,13 @@ static int __init arm64_enable_runtime_services(void)
 						   sizeof(efi_system_table_t));
 	if (!efi.systab) {
 		pr_err("Failed to remap EFI System Table\n");
-		return -1;
+		return -ENOMEM;
 	}
 	set_bit(EFI_SYSTEM_TABLES, &efi.flags);
 
 	if (!efi_virtmap_init()) {
 		pr_err("No UEFI virtual mapping was installed -- runtime services will not be available\n");
-		return -1;
+		return -ENOMEM;
 	}
 
 	/* Set up runtime services function pointers */