sched/headers: Remove <linux/sched.h> and <linux/slab.h> from <linux/delayacct.h>

The <linux/delayacct.h> file is a self-contained header and users of
it either don't need <linux/sched.h> and <linux/slab.h> - or have
already included it.

This reduces the size of the header dependency graph.
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

include/linux/delayacct.h

@@ -18,8 +18,6 @@
 #define _LINUX_DELAYACCT_H
 
 #include <uapi/linux/taskstats.h>
-#include <linux/sched.h>
-#include <linux/slab.h>
 
 /*
  * Per-task flags relevant to delay accounting

include/linux/fault-inject.h

@@ -61,6 +61,8 @@ static inline struct dentry *fault_create_debugfs_attr(const char *name,
 
 #endif /* CONFIG_FAULT_INJECTION */
 
+struct kmem_cache;
+
 #ifdef CONFIG_FAILSLAB
 extern bool should_failslab(struct kmem_cache *s, gfp_t gfpflags);
 #else