mfd: intel-m10-bmc: Add PMCI driver

Add the mfd driver for the Platform Management Component Interface
(PMCI) based interface of Intel MAX10 BMC controller.

PMCI is a software-visible interface, connected to card BMC which
provided the basic functionality of read/write BMC register. The access
to the register is done indirectly via a hardware controller/bridge
that handles read/write/clear commands and acknowledgments for the
commands.

Previously, intel-m10-bmc provided sysfs under
/sys/bus/spi/devices/... which is generalized in this change because
not all MAX10 BMC appear under SPI anymore.

Co-developed-by: Tianfei zhang <tianfei.zhang@intel.com>
Signed-off-by: Tianfei zhang <tianfei.zhang@intel.com>
Co-developed-by: Russ Weight <russell.h.weight@intel.com>
Signed-off-by: Russ Weight <russell.h.weight@intel.com>
Co-developed-by: Matthew Gerlach <matthew.gerlach@linux.intel.com>
Signed-off-by: Matthew Gerlach <matthew.gerlach@linux.intel.com>
Reviewed-by: Xu Yilun <yilun.xu@intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/20230116100845.6153-11-ilpo.jarvinen@linux.intel.com