spi.h and spi_legacy.h documentation conflicts

[dbkinder]

There are types and function names duplicated by these two include files that are causing the doxygen-generated API docs to be confused (material from both .h files is being combined into one since the names are the same). Are both .h files needed?

[nashif]

need to exclude spi_legacy.h, no need to show it, the right header to show is spi.h