Switched to int32_t for RSSI representation to allow running the code also
on devices with limited resources. Defined a new ad-hoc type to still keep
the possibility of using floating points on more capable devices.
Stub drivers provide a safe default implementation of the OpenRTX interface
APIs and can be used both as a starting point to implement the actual drivers
and to allow compiling binary images without needing to provide an actual
implementation first.
Silvano Seva