Create field filters for gsm_rr_csn_HL_flag() usages.

Change-Id: I74f110b477a3bf7e0c374db3147604d50018deba
Reviewed-on: https://code.wireshark.org/review/4435
Reviewed-by: Michael Mann <mmann78@netscape.net>
Petri-Dish: Michael Mann <mmann78@netscape.net>
Reviewed-by: Anders Broman <a.broman58@gmail.com>