By default, the peripheral clock for UART and SPI is set to 48 MHz and will
not be affected by the MCU clock change. This can be changed by a second
argument to `machine.freq(freq, peripheral_freq)`. The second argument
must be either 48 MHz or identical with the first argument.
Note that UART and SPI baud rates may have to be re-configured after
changing the MCU clock.
Signed-off-by: robert-hh <robert@hammelrath.com>
7270b871c2