Bootloader: Add support for ext2 blocks up to 4 KiB

This should work with blocks bigger than that, but my linux system
only supports up to 4 KiB, so I cannot test this.

This allows getting rid of forced block size in mkfs and let the
program select appropriately sized blocks.

script/image-create.sh

@@ -87,7 +87,7 @@ sudo partprobe $LOOP_DEV
 PARTITION1=${LOOP_DEV}p1
 PARTITION2=${LOOP_DEV}p2
 
-sudo mkfs.ext2 -q -b 1024 $PARTITION2
+sudo mkfs.ext2 -q $PARTITION2
 
 sudo mkdir -p $MOUNT_DIR || { echo "Failed to create banan mount dir."; exit 1; }