acpi: Clean IASL generated intermediate files

For boards that support ACPI, there are dsdt.aml, dsdt.asl.tmp and
dsdt.c in the board directory after a successful build. These are
intermediate files generated by IASL, and should be removed during
a 'make clean'.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

Makefile

@@ -1452,6 +1452,7 @@ clean: $(clean-dirs)
 		-o -name '.*.d' -o -name '.*.tmp' -o -name '*.mod.c' \
 		-o -name '*.symtypes' -o -name 'modules.order' \
 		-o -name modules.builtin -o -name '.tmp_*.o.*' \
+		-o -name 'dsdt.aml' -o -name 'dsdt.asl.tmp' -o -name 'dsdt.c' \
 		-o -name '*.gcno' \) -type f -print | xargs rm -f
 
 # mrproper - Delete all generated files, including .config