staging: comedi: me4000: usleep_range is preferred over udelay

Fix checkpatch issue: "CHECK: usleep_range is preferred over udelay; see
Documentation/timers/timers-howto.txt".  `udelay()` is only used in the
firmware upload process.  Replace them with `usleep_range()` with a
reasonable upper limit.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>