microblaze: Makefile cleanups

If CONFIG_INITRAMFS_SOURCE is set, "scripts/gen_initramfs_list.sh"
checks if the cpio image exists. Remove the duplicate check from the
Makefile.

Remove the "clean-kernel" variable which is unused in the Makefile and
is not used by the Kbuild.
Signed-off-by: Arun Bhanu <arun@bhanu.net>
Signed-off-by: Michal Simek <monstr@monstr.eu>

arch/microblaze/boot/Makefile

@@ -23,8 +23,6 @@ $(obj)/system.dtb: $(obj)/$(DTB).dtb
 endif
 
 $(obj)/linux.bin: vmlinux FORCE
-	[ -n $(CONFIG_INITRAMFS_SOURCE) ] && [ ! -e $(CONFIG_INITRAMFS_SOURCE) ] && \
-	touch $(CONFIG_INITRAMFS_SOURCE) || echo "No CPIO image"
 	$(call if_changed,objcopy)
 	$(call if_changed,uimage)
 	@echo 'Kernel: $@ is ready' ' (#'`cat .version`')'
@@ -62,6 +60,4 @@ quiet_cmd_dtc = DTC     $@
 $(obj)/%.dtb: $(dtstree)/%.dts FORCE
 	$(call if_changed,dtc)
 
-clean-kernel += linux.bin linux.bin.gz simpleImage.*
-
 clean-files += *.dtb simpleImage.*.unstrip linux.bin.ub