Some PWMOut pins on STM32F405 run at half frequency

[dhalbert]

True in 8.0.0-beta.1 on Feather STM32F405.

import pwmio, board
a1 = pwmio.PWMOut(board.A1, duty_cycle=32768, frequency=1000)
d5 = pwmio.PWMOut(board.D5, duty_cycle=32768, frequency=1000)
d6 = pwmio.PWMOut(board.D6, duty_cycle=32768, frequency=1000)
d9 = pwmio.PWMOut(board.D9, duty_cycle=32768, frequency=1000)
d10 = pwmio.PWMOut(board.D10, duty_cycle=32768, frequency=1000)
a3 = pwmio.PWMOut(board.A3, duty_cycle=32768, frequency=1000)
while True:
    pass

A1 runs at 500 Hz; D5 runs at the (proper) 1 kHz; another one runs at 2kHz; others are OK.

Thanks to SleeplessHeart from https://forums.adafruit.com/viewtopic.php?p=943799.