arm/efi: address MISRA C:2012 Rule 8.4

the function 'fdt_add_uefi_nodes' can be defined static, as its
only callers are within the same file. This in turn avoids
violating Rule 8.4 because no declaration is present.

No functional change.

Fixes: 6d70ea10d4 ("Add ARM EFI boot support”)
Signed-off-by: Nicola Vetrini <nicola.vetrini@bugseng.com>
Reviewed-by: Luca Fancellu <luca.fancellu@arm.com>
Acked-by: Stefano Stabellini <sstabellini@kernel.org>

xen/arch/arm/efi/efi-boot.h

@@ -227,7 +227,7 @@ static EFI_STATUS __init efi_process_memory_map_bootinfo(EFI_MEMORY_DESCRIPTOR *
  * of the System table address, the address of the final EFI memory map,
  * and memory map information.
  */
-EFI_STATUS __init fdt_add_uefi_nodes(EFI_SYSTEM_TABLE *sys_table,
+static EFI_STATUS __init fdt_add_uefi_nodes(EFI_SYSTEM_TABLE *sys_table,
                                             void *fdt,
                                             EFI_MEMORY_DESCRIPTOR *memory_map,
                                             UINTN map_size,