Remove clean commands that removed generated files in src/
Remove clean commands that removed generated files in src/

For a while now, generated files are not clobbering the
source directory anymore, so this temporary measure can
be removed.

Signed-off-by: Henner Zeller <259ad50fabbfd39355f36ecd6c0afca541ea66ef@acm.org>

chipsalliance/Surelog,alainmarcel/Surelog,chipsalliance/Surelog,alainmarcel/Surelog,chipsalliance/Surelog,alainmarcel/Surelog,chipsalliance/Surelog,alainmarcel/Surelog