docs: basics.rst: move kernel-doc workqueue markups to workqueue.rst

As there's already a rst file with workqueue markups, containing
part of them, move the other definitions, in order to avoid
warnings with Sphinx.
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

Documentation/core-api/workqueue.rst

@@ -396,3 +396,5 @@ Kernel Inline Documentations Reference
 ======================================
 
 .. kernel-doc:: include/linux/workqueue.h
+
+.. kernel-doc:: kernel/workqueue.c

Documentation/driver-api/basics.rst

@@ -55,15 +55,6 @@ High-resolution timers
 .. kernel-doc:: kernel/time/hrtimer.c
    :export:
 
-Workqueues and Kevents
-----------------------
-
-.. kernel-doc:: include/linux/workqueue.h
-   :internal:
-
-.. kernel-doc:: kernel/workqueue.c
-   :export:
-
 Internal Functions
 ------------------