iio: adc: ad4000: Use device specific timing for SPI transfers

The SPI transfers for AD4020, AD4021, and AD4022 have slightly different
timing specifications. Use device specific timing constraints to set SPI
transfer parameters. While tweaking time constraints, remove time related
defines including unused AD4000_TQUIET1_NS.

Signed-off-by: Marcelo Schmitt <marcelo.schmitt@analog.com>
Reviewed-by: David Lechner <dlechner@baylibre.com>
Link: https://patch.msgid.link/a36fcf44cc00b2a498170e2ae3f005829d516266.1733147444.git.marcelo.schmitt@analog.com


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