Makefile: add Rockchip idbloader.img to CLEAN_FILES

This file is generated in the root during Rockchip builds and so should
be cleaned up.
Signed-off-by: NThomas Hebb <tommyhebb@gmail.com>
Reviewed-by: NMichael Trimarchi <michael@amarulasolutions.com>

Makefile

@@ -1931,7 +1931,8 @@ CLEAN_DIRS  += $(MODVERDIR) \
 CLEAN_FILES += include/bmp_logo.h include/bmp_logo_data.h tools/version.h \
 	       boot* u-boot* MLO* SPL System.map fit-dtb.blob* \
 	       u-boot-ivt.img.log u-boot-dtb.imx.log SPL.log u-boot.imx.log \
-	       lpc32xx-* bl31.c bl31.elf bl31_*.bin image.map tispl.bin*
+	       lpc32xx-* bl31.c bl31.elf bl31_*.bin image.map tispl.bin* \
+	       idbloader.img
 
 # Directories & files removed with 'make mrproper'
 MRPROPER_DIRS  += include/config include/generated spl tpl \