recipetool: make plugin registration function name consistent with devtool
This should have been register_commands rather than register_command;
I used register_commands in devtool so lets change this here to be
consistent with that. (Since this is extensible through layers though we
need to remain compatible with the old name, so fall back to that if the
new function name isn't there.)
Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com> Signed-off-by: Ross Burton <ross.burton@intel.com>
