uml: delete unused code

Get rid of a bunch of unused stuff -
	cpu_feature had no users
	linux_prog is little-used, so its declaration is moved to the
user for easy deletion when the whole file goes away
	a long-unused debugging aid in helper.c is gone

Signed-off-by: Jeff Dike <jdike@addtoit.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/um/kernel/tt/gdb.c

@@ -115,6 +115,8 @@ struct gdb_data {
 	int err;
 };
 
+extern char *linux_prog;
+
 static void config_gdb_cb(void *arg)
 {
 	struct gdb_data *data = arg;