staging: IIO: IMU: ADIS16400: Add delay after self test

Add delay after self test to satisfy timing requirements.
Increase start-up delay.

Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Acked-by: Jonathan Cameron <jic23@cam.ac.uk>
CC: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>