ionic: shorter dev cmd wait time

Shorten our msleep time while polling for the dev command
request to finish.  Yes, checkpatch.pl complains that the
msleep might actually go longer - that won't hurt, but we'll
take the shorter time if we can get it.

Signed-off-by: Shannon Nelson <snelson@pensando.io>
Signed-off-by: David S. Miller <davem@davemloft.net>