Rework pwm temperature mapping

Rework pwm temperature mapping

Various chips have different numbers of valid values for pwm temperature
mapping. Rework the code to take this into account.

No longer keep map as bitmap, but maintain it as number 1..X. Do not try to
define a separate mapping entry for pwm4..6 on chips where the temperature
map for those pwm controls is taken from a different temperature input.
Introduce helpers to convert the control register contents to a map and
vice versa.

Reflect that IT8607 uses the new temperature map in bit 3..5 of the pwm
control register.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>