The driver never uses the IRQ1_CFG register so there's no need to provide
a default value. It's set as a readable register only for debugging
through the regmap registers file.

A system-specific firmware could overwrite this register with a non-default
value. Therefore the driver can't hardcode what the initial value actually
is. As the register is only for debugging the value can be left unknown
until someone wants to read it through debugfs.
Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Link: https://lore.kernel.org/r/20240209145700.1555950-1-rf@opensource.cirrus.comSigned-off-by: Mark Brown <broonie@kernel.org>