ubifs: remove breaking commas from ubi calls

The extra commas get output by the shell resulting in errors since
the commands that get called with those extra commas are then
malformed.

Signed-off-by: Joris de Vries <joris@apptrician.nl>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@38419 3c298f89-4303-0410-b956-a3cf2f4a3e73