Add support for g761 PWM Fan Controller.

The g761 is a copy of the g763 with the only difference of supporting
and internal clock. The internal clock is used if no clocks property is
defined in device node and in such case the required bit is enabled and
clock handling is skipped.

The internal clock oscillator runs at 31KHz.
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
Link: https://lore.kernel.org/r/20240604164348.542-3-ansuelsmth@gmail.comSigned-off-by: Guenter Roeck <linux@roeck-us.net>