qf: Move "setup" from case to new subcommand.

No functional change, only moving from the
case to its own function, with the arguments now shifted.

It seems that the argument for branch_init is useles,
but I will keep it for now to avoid any change
that is not related to the new subcommand scheme.

Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Jani Nikula <jani.nikula@intel.com>