mk/image.mk: Fix calling mkfs.jffs2

This command does not reside in ${STAGING_HOST_DIR}/usr/bin (anymore?),
also setting PATH='${HOST_PATH}' prior to just calling the command
without path is more elegant in my opinion.

Signed-off-by: Phil Sutter <phil@nwl.cc>

mk/image.mk

@@ -188,7 +188,7 @@ ${BUILD_DIR}/root.squashfs: ${TARGET_DIR}/.adk
 		-nopad -noappend -root-owned $(MAKE_TRACE)
 
 ${FW_DIR}/${ROOTFSJFFS2}: ${TARGET_DIR}
-	${STAGING_HOST_DIR}/usr/bin/mkfs.jffs2 $(ADK_JFFS2_OPTS) -q -r ${TARGET_DIR} \
+	PATH='${HOST_PATH}' mkfs.jffs2 $(ADK_JFFS2_OPTS) -q -r ${TARGET_DIR} \
 		--pad=$(ADK_TARGET_MTD_SIZE) -o ${FW_DIR}/${ROOTFSJFFS2} $(MAKE_TRACE)
 
 createinitramfs: ${STAGING_TARGET_DIR}/${INITRAMFS}_list