spi: spidev_test: Remove the whole "include" directory when make clean

In the current code, it only removes "include/linux/spi/spidev.h" file
when make clean and there still exists useless "include/linux/spi/"
directory, just remove it.
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Link: https://lore.kernel.org/r/1581567368-8055-4-git-send-email-yangtiezhu@loongson.cnSigned-off-by: Mark Brown <broonie@kernel.org>

tools/spi/Makefile

@@ -51,7 +51,7 @@ $(OUTPUT)spidev_fdx: $(SPIDEV_FDX_IN)
 
 clean:
 	rm -f $(ALL_PROGRAMS)
-	rm -f $(OUTPUT)include/linux/spi/spidev.h
+	rm -rf $(OUTPUT)include/
 	find $(if $(OUTPUT),$(OUTPUT),.) -name '*.o' -delete -o -name '\.*.d' -delete
 
 install: $(ALL_PROGRAMS)