[legal] Add the MIT and ISC licenses to licence.pl

The MIT and ISC licenses are legally equivalent to the bsd2 license,
but with slightly different verbiage.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Michael Brown <mcb30@etherboot.org>

src/util/licence.pl

       public_domain => 1,
       bsd3 => 1,
       bsd2 => 1,
+      mit  => 1,
+      isc  => 1,
     },
   },
   gpl2_or_later => {
       public_domain => 1,
       bsd3 => 1,
       bsd2 => 1,
+      mit  => 1,
+      isc  => 1,
     },
   },
   gpl2_only => {
       public_domain => 1,
       bsd3 => 1,
       bsd2 => 1,
+      mit  => 1,
+      isc  => 1,
     },
   },
   public_domain => {
       public_domain => 1,
       bsd3 => 1,
       bsd2 => 1,
+      mit  => 1,
+      isc  => 1,
     },
   },
   bsd3 => {
     can_subsume => {
       public_domain => 1,
       bsd2 => 1,
+      mit  => 1,
+      isc  => 1,
     },
   },
   bsd2 => {
     desc => "BSD Licence (without advertising or endorsement clauses)",
+    can_subsume => {
+      public_domain => 1,
+      mit  => 1,
+      isc  => 1,
+    },
+  },
+  mit => {
+    desc => "MIT/X11/Xorg Licence",
+    can_subsume => {
+      public_domain => 1,
+      isc => 1,
+    },
+  },
+  isc => {
+    desc => "ISC Licence",
     can_subsume => {
       public_domain => 1,
     },