iio: imu: inv_icm42600: add register caching in the regmap

Register caching is improving bus access a lot because of the register
window bank setting. Previously, bank register was set for every
register access. Now with caching, it happens only when changing bank
which is very infrequent.

Signed-off-by: Jean-Baptiste Maneyrol <jean-baptiste.maneyrol@tdk.com>
Link: https://lore.kernel.org/r/20240607081039.789079-1-inv.git-commit@tdk.com


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