ath79: bsap18x0: pad rootfs image

This image is supposed to be written with help of bootloader to the
flash, but as it stands, it's not aligned to block size and RedBoot will
happily create non-aligned partition size in FIS directory. This could
lead to kernel to mark the partition as read-only, therefore pad the
image to block erase size boundary.

Signed-off-by: Tomasz Maciej Nowak <tmn505@gmail.com>

target/linux/ath79/image/generic.mk

@@ -209,7 +209,7 @@ define Device/adtran_bsap1880
   IMAGE_SIZE := 11200k
   IMAGES += kernel.bin rootfs.bin
   IMAGE/kernel.bin := append-kernel
-  IMAGE/rootfs.bin := append-rootfs | pad-rootfs
+  IMAGE/rootfs.bin := append-rootfs | pad-rootfs | pad-to $$(BLOCKSIZE)
   IMAGE/sysupgrade.bin := append-rootfs | pad-rootfs | \
 	check-size | sysupgrade-tar rootfs=$$$$@ | append-metadata
 endef