fs/squashfs: split commands

Now that we can properly printf a multi-line command, there is no need
to use a single command to gnerate the squashfs image.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

fs/squashfs/squashfs.mk

@@ -26,7 +26,7 @@ endif
 
 define ROOTFS_SQUASHFS_CMD
 	$(HOST_DIR)/usr/bin/mksquashfs $(TARGET_DIR) $@ -noappend \
-		$(ROOTFS_SQUASHFS_ARGS) && \
+		$(ROOTFS_SQUASHFS_ARGS)
 	chmod 0644 $@
 endef