Merge port and gpio definitions into one file in the DRV layer

Merge port and gpio definitions into one file in the DRV layer

The idea is to have the pin and port names in a separated target specific
header files, the pin and port definitions in a target specific source files and
the target independent functions and data types in a common header and source
files.

The application than should include only one header file digital_io_def.h,
where are defined the names of the pins, and digital_io.h where is defined the
driver interface.