Move list types from <linux/list.h> to <linux/types.h>.

This allows a list_head (or hlist_head, etc.) to be used from places
that used to be impractical, in particular <asm/processor.h>, which
used to cause include file recursion: <linux/list.h> includes
<linux/prefetch.h>, which always includes <asm/processor.h> for the
prefetch macros, as well as <asm/system.h>, which often includes
<asm/processor.h> directly or indirectly.

This avoids a lot of painful workaround hackery on the tile
architecture, where we use a list_head in the thread_struct to chain
together tasks that are activated on a particular hardwall.

Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
Reviewed-by: Matthew Wilcox <willy@linux.intel.com>

include/linux/types.h

@@ -197,6 +197,18 @@ typedef struct {
 } atomic64_t;
 #endif
 
+struct list_head {
+	struct list_head *next, *prev;
+};
+
+struct hlist_head {
+	struct hlist_node *first;
+};
+
+struct hlist_node {
+	struct hlist_node *next, **pprev;
+};
+
 struct ustat {
 	__kernel_daddr_t	f_tfree;
 	__kernel_ino_t		f_tinode;