Add make clean option for bootloader build

Change-Id: I5f51d36055a65333b8918fce541b187084623308
Signed-off-by: John Stultz <john.stultz@linaro.org>
diff --git a/bootloader/Makefile b/bootloader/Makefile
index 4d0f031..3ecc46e 100644
--- a/bootloader/Makefile
+++ b/bootloader/Makefile
@@ -27,3 +27,7 @@
 	ln -sf $(EDK2_DIR)/Build/HiKey/RELEASE_GCC49/FV//bl1.bin && \
 	make CROSS_COMPILE=arm-linux-androideabi- l-loader.bin && \
 	mv l-loader.bin $(DIST_DIR)/
+
+clean:
+	rm -rf $(DIST_DIR)/fip.bin $(DIST_DIR)/l-loader.bin
+