Add Xuelin iHIFI 770/770C/800 support

Taken from the xvortex fork (Roman Stolyarov)
Ported, rebased, and cleaned up by myself.

Change-Id: I7b2bca2d29502f2e4544e42f3d122786dd4b7978

tools/builds.pm

@@ -422,6 +422,18 @@ $releasenotes="/wiki/ReleaseNotes314";
         name => 'xDuoo X3',
         status => 2,
     },
+    'ihifi770' => {
+        name => 'Xuelin iHIFI 770',
+        status => 2,
+    },
+    'ihifi770C' => {
+        name => 'Xuelin iHIFI 770C',
+        status => 2,
+    },
+    'ihifi800' => {
+        name => 'Xuelin iHIFI 800',
+        status => 2,
+    },
 );
 
 sub manualname {