verification/rvgen: Fix options shared among commands

verification/rvgen: Fix options shared among commands

After rvgen was refactored to use subparsers, the common options (-a and
-D) were left in the main parser. This meant that they needed to be
called /before/ the subcommand and using them without subcommand was
allowed. This is not the original intent.

  rvgen -D "some description" container -n name

Define the options as parent in the subparsers to allow them to be used
from both subcommands together with other options.

  rvgen container -n name -D "some description"

Fixes: 5270a0e3041c ("verification/dot2k: Replace is_container() hack with subparsers")
Reviewed-by: Nam Cao <namcao@linutronix.de>
Link: https://lore.kernel.org/r/20260514152055.229162-7-gmonaco@redhat.com
Signed-off-by: Gabriele Monaco <gmonaco@redhat.com>