image: adapt mikrotik yafut to allow switch to bootimage YAFFS path

Adjust the YAFFS file path written depending on the sysupgrade
filename.
Default to kernel (for ELF), switch to bootimage (for NPK) if image name
has v7.

Signed-off-by: John Thomson <[email protected]>

include/image-commands.mk

@@ -519,7 +519,7 @@ define Build/yaffs-filesystem
 		filesystem_size="filesystem_blocks * 64 * 1024" \
 		filesystem_size_with_reserve="(filesystem_blocks + 2) * 64 * 1024"; \
 		head -c $$filesystem_size_with_reserve /dev/zero | tr "\000" "\377" > [email protected] \
-		&& yafut -d [email protected] -w -i $@ -o kernel -C 1040 -B 64k -E -P -S $(1) \
+		&& yafut -d [email protected] -w -i $@ -o $(if $(findstring v7,$@),bootimage,kernel) -C 1040 -B 64k -E -P -S $(1) \
 		&& truncate -s $$filesystem_size [email protected] \
 		&& mv [email protected] $@
 endef