docs: fix broken references to text files

Several references got broken due to txt to ReST conversion.

Several of them can be automatically fixed with:

	scripts/documentation-file-ref-check --fix

Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org> # hwtracing/coresight/Kconfig
Reviewed-by: Paul E. McKenney <paulmck@kernel.org> # memory-barrier.txt
Acked-by: Alex Shi <alex.shi@linux.alibaba.com> # translations/zh_CN
Acked-by: Federico Vaga <federico.vaga@vaga.pv.it> # translations/it_IT
Acked-by: Marc Zyngier <maz@kernel.org> # kvm/arm64
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/6f919ddb83a33b5f2a63b6b5f0575737bb2b36aa.1586881715.git.mchehab+huawei@kernel.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

mm/gup.c

@@ -2843,9 +2843,9 @@ EXPORT_SYMBOL_GPL(get_user_pages_fast);
  * the arguments here are identical.
  *
  * FOLL_PIN means that the pages must be released via unpin_user_page(). Please
- * see Documentation/vm/pin_user_pages.rst for further details.
+ * see Documentation/core-api/pin_user_pages.rst for further details.
  *
- * This is intended for Case 1 (DIO) in Documentation/vm/pin_user_pages.rst. It
+ * This is intended for Case 1 (DIO) in Documentation/core-api/pin_user_pages.rst. It
  * is NOT intended for Case 2 (RDMA: long-term pins).
  */
 int pin_user_pages_fast(unsigned long start, int nr_pages,
@@ -2883,9 +2883,9 @@ EXPORT_SYMBOL_GPL(pin_user_pages_fast);
  * the arguments here are identical.
  *
  * FOLL_PIN means that the pages must be released via unpin_user_page(). Please
- * see Documentation/vm/pin_user_pages.rst for details.
+ * see Documentation/core-api/pin_user_pages.rst for details.
  *
- * This is intended for Case 1 (DIO) in Documentation/vm/pin_user_pages.rst. It
+ * This is intended for Case 1 (DIO) in Documentation/core-api/pin_user_pages.rst. It
  * is NOT intended for Case 2 (RDMA: long-term pins).
  */
 long pin_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm,
@@ -2919,9 +2919,9 @@ EXPORT_SYMBOL(pin_user_pages_remote);
  * FOLL_PIN is set.
  *
  * FOLL_PIN means that the pages must be released via unpin_user_page(). Please
- * see Documentation/vm/pin_user_pages.rst for details.
+ * see Documentation/core-api/pin_user_pages.rst for details.
  *
- * This is intended for Case 1 (DIO) in Documentation/vm/pin_user_pages.rst. It
+ * This is intended for Case 1 (DIO) in Documentation/core-api/pin_user_pages.rst. It
  * is NOT intended for Case 2 (RDMA: long-term pins).
  */
 long pin_user_pages(unsigned long start, unsigned long nr_pages,