1. kvm_cmd_run_init() appends "root=/dev/root" to real_cmdline if
   cfg.using_rootfs == T. This doesn't hurt but makes no sense and
   looks confusing.

   We do not need to initialiaze the kernel's saved_root_name[] and
   "/dev/root" means nothing to name_to_dev_t().

   We only need to pass this mount-tag to 9p but the kernel always
   uses dev_name="/dev/root" in mount_root() path, so we can safely
   remove this option from the command line.

2. "rw" in rootflags looks confusing too, it is silently ignored by
   v9fs_parse_options() and has no effect.

   We need to clear MS_RDONLY from root_mountflags, this is what the
   "standalone" kernel parameter correctly does.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>