iio: accel: adxl345: initialize FIFO delay value for SPI

Add the possibility to delay FIFO access when SPI is used. According to
the datasheet this is needed for the adxl345. When initialization
happens over SPI the need for delay is to be signalized, and the delay
will be used.

Signed-off-by: Lothar Rubusch <l.rubusch@gmail.com>
Link: https://patch.msgid.link/20241228232949.72487-3-l.rubusch@gmail.com


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>