x86: use targets in the boot Makefile instead of CLEAN_FILES

Impact: cleanup

Instead of using CLEAN_FILES in arch/x86/Makefile, add generated files
to targets in arch/x86/boot/Makefile, so they will get naturally
cleaned up by "make clean".

Cc: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

arch/x86/Makefile

@@ -194,7 +194,3 @@ define archhelp
   echo  '                  FDARGS="..."  arguments for the booted kernel'
   echo  '                  FDINITRD=file initrd for the booted kernel'
 endef
-
-CLEAN_FILES += arch/x86/boot/fdimage \
-	       arch/x86/boot/image.iso \
-	       arch/x86/boot/mtools.conf        

arch/x86/boot/Makefile

@@ -23,6 +23,7 @@ ROOT_DEV	:= CURRENT
 SVGA_MODE	:= -DSVGA_MODE=NORMAL_VGA
 
 targets		:= vmlinux.bin setup.bin setup.elf bzImage
+targets		+= fdimage fdimage144 fdimage288 image.iso mtools.conf
 subdir-		:= compressed
 
 setup-y		+= a20.o cmdline.o copy.o cpu.o cpucheck.o edd.o