.. this probably came from the examples that I studied at the beginning
of implementation.
The card detection feature is unused. As a "detect pin" is not
sent from the shared-bindings, there is no way to get the correct pin
anyway. Instead, if code needs to detect the insertion state it can
directly use the pin as GPIO in Python code.
Currently, only the bus specs of the stm32f405xx have been coded.
Other stm-family chips need (at a minimum) the specs added in their
periph.[ch] files.
