The script required the passing of option '-b' for setting up the
target to use a single MTD partition and multiple UBI volumes.
If a target however already has the variable 'ubisysvols' set to
'yes' but this parameter is forgotten when calling the script, the
partition layout would change to default (several MTD partitions).
Remove the recently added '-b' option and make the script decide
basing on the current value of 'ubisysvols' variable.
Signed-off-by: Hector Palacios <hector.palacios@digi.com>