spmi: add a spmi driver for Apple SoC

spmi: add a spmi driver for Apple SoC

The connected PMU contains several useful nvmem cells such as RTC offset,
boot failure counters, reboot/shutdown selector, and a few others.
In addition M3+ machines have their USB-PD controller connected via SPMI.

Signed-off-by: Jean-Francois Bortolotti <jeff@borto.fr>
Reviewed-by: Sven Peter <sven@svenpeter.dev>
Reviewed-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Co-developed-by: Sasha Finkelstein <fnkl.kernel@gmail.com>
Signed-off-by: Sasha Finkelstein <fnkl.kernel@gmail.com>
Link: https://lore.kernel.org/r/20250409-spmi-v4-2-eb81ecfd1f64@gmail.com
Reviewed-by: Neal Gompa <neal@gompa.dev>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
Link: https://lore.kernel.org/r/20250518032330.2959766-4-sboyd@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>