Make the openfirmware getchar entry point non-blocking. This catches up with jhb's 2005/05/27 loader multiple-console change.
Make the openfirmware getchar entry point non-blocking. This catches up
with jhb's 2005/05/27 loader multiple-console change.

Tested by: marius/sparc64, grehan/ofwppc

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase