hwmon: (pmbus/mp2975) Fix IRQ masking

hwmon: (pmbus/mp2975) Fix IRQ masking

The MP2971/MP2973 use a custom 16bit register format for
SMBALERT_MASK which doesn't follow the PMBUS specification.

Map the PMBUS defined bits used by the common code onto the custom
format used by MPS and since the SMBALERT_MASK is currently never read
by common code only implement the mapping for write transactions.

Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Signed-off-by: Naresh Solanki <naresh.solanki@9elements.com>
Link: https://lore.kernel.org/r/20240318174406.3782306-1-naresh.solanki@9elements.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>