iio: accel: fxls8962af: fix errata bug E3 - I2C burst reads

When flushing the hw fifo there is a bug in the I2C that prevents burst
reads of more than one sample pair.

Signed-off-by: Sean Nyekjaer <sean@geanix.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>