fix rebuild issue for zimage target

mk/kernel-build.mk

@@ -7,6 +7,10 @@ include ${TOPDIR}/mk/kernel-vars.mk
 
 KERNEL_FILE:=$(ADK_TARGET_KERNEL)
 KERNEL_TARGET:=$(ADK_TARGET_KERNEL)
+ifeq ($(ADK_TARGET_KERNEL_ZIMAGE),y)
+KERNEL_FILE:=vmlinux
+KERNEL_TARGET:=$(ADK_TARGET_KERNEL)
+endif
 ifeq ($(ADK_TARGET_KERNEL_BZIMAGE),y)
 KERNEL_FILE:=vmlinux
 KERNEL_TARGET:=all