staging: dgnc: Fix usleep_range is preferred over udelay

This patch fixes the issue:

CHECK: usleep_range is preferred over udelay; see
Documentation/timers/timers-howto.txt

Signed-off-by: Joshua Abraham <j.abraham1776@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>