signal: Kill bogus dependency on list.h

list_head is in types.h, not list.h.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

include/linux/signal.h

@@ -3,6 +3,7 @@
 #define _LINUX_SIGNAL_H
 
 #include <linux/bug.h>
+#include <linux/list.h>
 #include <linux/signal_types.h>
 #include <linux/string.h>
 

include/linux/signal_types.h

@@ -6,7 +6,7 @@
  * Basic signal handling related data type definitions:
  */
 
-#include <linux/list.h>
+#include <linux/types.h>
 #include <uapi/linux/signal.h>
 
 typedef struct kernel_siginfo {