staging: dgap: removes references to mgmt code

This patch removes references to mgmt functions from
the code. The files mgmt.c and mgmt.h will be
removed in the patches that follow.

Signed-off-by: Lidza Louina <lidza.louina@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>