staging: dgnc: dgnc_cls.c: Replaced udelay by usleep_range

This patch is to file dgnc_cls.c that fixes up udelay function by
usleep_range.
It is safe to use according to the following documentation
Documentation/timers/timers-howto.txt. So that is why I have given
an appropriate time range.

Signed-off-by: Jitendra Kumar Khasdev <jkhasdev@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>