Fix option type comments for CMDARG_EARLYINIT_FILE and CMDARG_EARLYINIT_COMMAND.

The comments in the enum cmdarg_kind were using -sx and -sex instead
of -eix and -eiex.

(Note that gdb --help does not speak about these options).

(pushed as obvious)

gdb/main.c

@@ -574,14 +574,14 @@ enum cmdarg_kind
 
   /* Option type -ix.  */
   CMDARG_INIT_FILE,
-    
+
   /* Option type -iex.  */
   CMDARG_INIT_COMMAND,
 
-  /* Option type -sx.  */
+  /* Option type -eix.  */
   CMDARG_EARLYINIT_FILE,
 
-  /* Option type -sex.  */
+  /* Option type -eiex.  */
   CMDARG_EARLYINIT_COMMAND
 };