staging: iio: resolver: ad2s1210: do not use fault register for dummy read

When reading registers on the AD2S1210 chip, we have to supply a "dummy"
address for the second SPI tx byte so that we don't accidentally write
to a register. This register will be read and the value discarded on the
next regmap read or write call.

Reading the fault register has a side-effect of clearing the faults
so we should not use this register for the dummy read.

Signed-off-by: David Lechner <dlechner@baylibre.com>
Link: https://lore.kernel.org/r/20231005-ad2s1210-mainline-v4-1-ec00746840fc@baylibre.com


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