Staging: olpc_dcon: change to msleep to usleep_range

The resolution of msleep is related to HZ, so with HZ set to
100 any msleep of less then 10ms will become ~10ms. This is
not what we want. Use usleep_range to get more control of
what is happening here.

Signed-off-by: Jens Frederich <jfrederich@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>