arm: Allow supporting ACPI-table generation

Some ARM boards are using ACPI now. It seems that U-Boot should support
this method. Add ARM to the list of archs which can generate ACPI tables.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/Kconfig b/arch/Kconfig
index b5aa83d..c9608cd 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -62,6 +62,7 @@
 	select ARCH_SUPPORTS_LTO
 	select CREATE_ARCH_SYMLINK
 	select HAVE_PRIVATE_LIBGCC if !ARM64
+	select SUPPORT_ACPI
 	select SUPPORT_OF_CONTROL
 
 config M68K