makefile: not need to regenerate kernel.release file when make kernelrelease

Brice reported that 'kernelrelease' has a dependence on include/config/kernel.release,
causes this file to be regenerated every time when invoke it. It doesn't have to.
Reported-by: NBrice Goglin <Brice.Goglin@inria.fr>
Tested-by: NBrice Goglin <Brice.Goglin@inria.fr>
Signed-off-by: NWANG Cong <amwang@redhat.com>
Signed-off-by: NMichal Marek <mmarek@suse.cz>

Makefile

@@ -1408,8 +1408,8 @@ checkstack:
 	$(OBJDUMP) -d vmlinux $$(find . -name '*.ko') | \
 	$(PERL) $(src)/scripts/checkstack.pl $(CHECKSTACK_ARCH)
 
-kernelrelease: include/config/kernel.release
-	@echo $(KERNELRELEASE)
+kernelrelease:
+	@echo "$(KERNELVERSION)$$($(CONFIG_SHELL) $(srctree)/scripts/setlocalversion $(srctree))"
 
 kernelversion:
 	@echo $(KERNELVERSION)