imx6: images: ventana: change name of ubi output

imx6: images: ventana: change name of ubi output

Change the name of the .ubi produced to strip out the word 'factory'. This is
mainly due to the fact that there is no difference between the Ventana 'factory'
image vs the standard image.

Name changes from:
openwrt-imx6-ventana-squashfs.nand-factory_<size>.ubi to
openwrt-imx6-ventana-squashfs-nand_<size>.ubi

Signed-off-by: Pushpal Sidhu <psidhu@gateworks.com>
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@48016 3c298f89-4303-0410-b956-a3cf2f4a3e73