Set the rlc len field before we try to use it in an expert info.

Conflicts:
	epan/dissectors/packet-rlc.c

Bug:9795
Change-Id: I740a9fe36278995cf6e590206f600c037789f0eb
Reviewed-on: https://code.wireshark.org/review/2344
Reviewed-by: Evan Huus <eapache@gmail.com>
(cherry picked from commit ba6eb5c72ffe82ca0e51c7083240975a5b118ad2)
Reviewed-on: https://code.wireshark.org/review/2345
(cherry picked from commit 2c877e0c77be47f5ac78b8f307081b5e4f36b2be)
Reviewed-on: https://code.wireshark.org/review/2346
Reviewed-on: https://code.wireshark.org/review/3439
Reviewed-by: Balint Reczey <balint@balintreczey.hu>