[source] build: add image command for calling kernel2minor

[LEDE Commits]

nbd pushed a commit to source.git, branch master:
https://git.lede-project.org/c2e6ca26e52d1675ed1d9c7edbde257817806176

commit c2e6ca26e52d1675ed1d9c7edbde257817806176
Author: Felix Fietkau <nbd at nbd.name>
AuthorDate: Fri Jan 6 16:49:52 2017 +0100

    build: add image command for calling kernel2minor
    
    Signed-off-by: Felix Fietkau <nbd at nbd.name>
---
 include/image-commands.mk | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/include/image-commands.mk b/include/image-commands.mk
index 083a389..a7acd0e 100644
--- a/include/image-commands.mk
+++ b/include/image-commands.mk
@@ -190,3 +190,8 @@ metadata_json = \
 define Build/append-metadata
 	$(if $(SUPPORTED_DEVICES),echo $(call metadata_json,$(SUPPORTED_DEVICES)) | fwtool -I - $@)
 endef
+
+define Build/kernel2minor
+	kernel2minor -k $@ -r $@.new $(1)
+	mv $@.new $@
+endef