Vlv2TbltDevicePkg: Only sort boot options when necessary

* PlatformBootManagerAfterConsole() always sorted the boot options at
  the end, and this would invalidate the BootOrder created by the user.
  Besides, the current implementation would sort the boot options twice,
  and this is not efficient. We should just sort the boot options once
  at the end of the function only for the very first boot.

* Update the string in IsNeedSortBootOption() to match the description
  of BootManagerMenuApp.

Cc: Zailiang Sun <zailiang.sun@intel.com>
Cc: Yi Qian <yi.qian@intel.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Signed-off-by: Gary Lin <glin@suse.com>
Reviewed-by: Michael D Kinney <michael.d.kinney@intel.com>