ASoC: Remove volatility from WM8900 POWER1 register

ASoC: Remove volatility from WM8900 POWER1 register

commit 6d212d8e86fb4221bd91b9266b7567ee2b83bd01 upstream.

Not all bits can be read back from POWER1 so avoid corruption when using
a read/modify/write cycle by marking it non-volatile - the only thing we
read back from it is the chip revision which has diagnostic value only.
We can re-add later but that's a more invasive change than is suitable
for a bugfix.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Liam Girdwood <lrg@slimlogic.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>