include: force a kernel-generated cpio removal and rebuild

Make sure that the kernel rebuilds the initramfs cpio archive file by
deleting it before so we get it re-generated properly.

Signed-off-by: Florian Fainelli <florian@openwrt.org>

SVN-Revision: 37125

include/kernel-defaults.mk

@@ -144,6 +144,7 @@ ifneq ($(CONFIG_TARGET_ROOTFS_INITRAMFS),)
 define Kernel/CompileImage/Initramfs
 	$(call Kernel/Configure/Initramfs)
 	$(if $(CONFIG_TARGET_ROOTFS_INITRAMFS),,rm -f $(TARGET_DIR)/init)
+	rm -rf $(KERNEL_BUILD_DIR)/usr/initramfs_data.cpio*
 	+$(MAKE) $(KERNEL_MAKEOPTS) $(subst ",,$(KERNELNAME))
 	#")
 	#")