kbuild: remove unused -r option for module-init-tool depmod

Following a thread on busybox mailing list
depmod -r option is ignored by module-init-tools depmod
-r option break busybox depmod.

So the best solution look to remove -r from kernel Makefile
Signed-off-by: Gilles Espinasse <g.esp@free.fr>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

Makefile

@@ -1543,7 +1543,7 @@ quiet_cmd_depmod = DEPMOD  $(KERNELRELEASE)
       cmd_depmod = \
 	if [ -r System.map -a -x $(DEPMOD) ]; then                              \
 		$(DEPMOD) -ae -F System.map                                     \
-		$(if $(strip $(INSTALL_MOD_PATH)), -b $(INSTALL_MOD_PATH) -r)   \
+		$(if $(strip $(INSTALL_MOD_PATH)), -b $(INSTALL_MOD_PATH) )     \
 		$(KERNELRELEASE);                                               \
 	fi