mm/headers, sched/headers: Move task related MM types from <linux/mm_types.> to <linux/mm_types_task.h>

Separate all the MM types that are embedded directly in 'struct task_struct'
into the <linux/mm_types_task.h> header.

The goal is to include this header in <linux/sched.h>, not the full <linux/mm_types.h>
header, to reduce the size, complexity and coupling of <linux/sched.h>.

(This patch does not change <linux/sched.h> yet.)

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>