binfmt: Refactor binfmt_exec.c This change also fixes an argv issue for CONFIG_SCHED_ONEXIT=n or CONFIG_SCHED_HAVE_PARENT=n Signed-off-by: Masayuki Ishikawa <Masayuki.Ishikawa@jp.sony.com> Approved-by: GregoryN <gnutt@nuttx.org>