elf: fix FDE Count formatting

Displays the FDE Count as a number, not a series of bytes.

Change-Id: I60dd426cb5305a5001a8200578008b7c4a99c64e
Reviewed-on: https://code.wireshark.org/review/5489
Reviewed-by: Peter Wu <peter@lekensteyn.nl>
Petri-Dish: Michal Labedzki <michal.labedzki@tieto.com>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Michal Labedzki <michal.labedzki@tieto.com>