iio: accel: fix ADXL355 startup race condition

iio: accel: fix ADXL355 startup race condition

There is an race-condition where device is not full working after SW reset.
Therefore it's necessary to wait some time after reset and verify shadow
registers values by reading and comparing the values before/after reset.
This mechanism is described in datasheet at least from revision D.

Fixes: 12ed27863ea3 ("iio: accel: Add driver support for ADXL355")
Signed-off-by: Valek Andrej <andrej.v@skyrain.eu>
Signed-off-by: Kessler Markus <markus.kessler@hilti.com>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>