platform/x86: oxpec: Adhere to sysfs-class-hwmon and enable pwm on 2

platform/x86: oxpec: Adhere to sysfs-class-hwmon and enable pwm on 2

Currently, the driver does not adhere to the sysfs-class-hwmon
specification: 0 is used for auto fan control and 1 is used for manual
control. However, it is expected that 0 sets the fan to full speed,
1 sets the fan to manual, and then 2 is used for automatic control.

Therefore, change the sysfs API to reflect this and enable pwm on 2.

As we are breaking the ABI for this driver, rename oxpec to oxp_ec,
reflecting the naming convention used by other drivers, to allow for
a smooth migration in current userspace programs.

Closes: https://lore.kernel.org/linux-hwmon/20241027174836.8588-1-derekjohn.clark@gmail.com/
Reviewed-by: Derek J. Clark <derekjohn.clark@gmail.com>
Reviewed-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Antheas Kapenekakis <lkml@antheas.dev>
Link: https://lore.kernel.org/r/20250425111821.88746-12-lkml@antheas.dev
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>