sched/headers: Remove the <linux/gfp.h> include from <linux/sched.h>

This reduces sched.h header dependencies.
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>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

include/linux/sched.h

@@ -22,7 +22,6 @@
 #include <linux/kcov.h>
 #include <linux/task_io_accounting.h>
 #include <linux/latencytop.h>
-#include <linux/gfp.h>
 #include <linux/topology.h>
 #include <linux/magic.h>