This sets the BLE key distribution parameters at runtime. This isn't
needed in most ports since we already set the default values in
`extmod/nimble/syscfg/syscfg.h`; however in the ESP32 port that
headerfile is not used, and the default values in the ESP-IDF don't
enable key distribution nor can we change those defaults via
`sdkconfig`. Thus we're setting these values explicitly at runtime.
Signed-off-by: Daniël van de Giessen <daniel@dvdgiessen.nl>