mpich: remove dragonegg and llvm subports

The llvm compiler has been blacklisted for a very long time now. Dragonegg
compilers have been broken for years.

science/mpich/Portfile

@@ -318,7 +318,7 @@ if {${subport} != ${name}} {
         revision                3
 
         compilers.choose   fc f77 f90
-        compilers.setup    -dragonegg default_fortran
+        compilers.setup    default_fortran
 
         if {[fortran_variant_isset]} {
             configure.args-delete   --disable-fortran