Update iso6392.txt

Add new es-MX option for the latin metadata search in  www.themoviedb.org

Content add: spa||es-mx|Spanish; Latin|espagnol; Latin

Emby.Server.Implementations/Localization/iso6392.txt

@@ -400,6 +400,7 @@ sog|||Sogdian|sogdien
 som||so|Somali|somali
 son|||Songhai languages|songhai, langues
 sot||st|Sotho, Southern|sotho du Sud
+spa||es-mx|Spanish; Latin|espagnol; Latin
 spa||es|Spanish; Castilian|espagnol; castillan
 srd||sc|Sardinian|sarde
 srn|||Sranan Tongo|sranan tongo