include/linux/llist.h: replace kernel.h with the necessary inclusions

When kernel.h is used in the headers it adds a lot into dependency hell,
especially when there are circular dependencies are involved.

Replace kernel.h inclusion with the list of what is really being used.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Andy Shevchenko <[e-mail]>
Cc: Boqun Feng <[e-mail]>
Cc: Brendan Higgins <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Jonathan Cameron <[e-mail]>
Cc: Laurent Pinchart <[e-mail]>
Cc: Mauro Carvalho Chehab <[e-mail]>
Cc: Miguel Ojeda <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Rasmus Villemoes <[e-mail]>
Cc: Sakari Ailus <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Cc: Thorsten Leemhuis <[e-mail]>
Cc: Waiman Long <[e-mail]>
Cc: Will Deacon <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

include/linux/llist.h

···
  */
 
 #include <linux/atomic.h>
-#include <linux/kernel.h>
+#include <linux/container_of.h>
+#include <linux/stddef.h>
+#include <linux/types.h>
 
 struct llist_head {
 	struct llist_node *first;