docs: core-api: add circular-buffers documentation

The circular-buffers.txt is already in ReST format. So, move it to the
core-api guide, where it belongs.
Signed-off-by: NMauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: NJonathan Corbet <corbet@lwn.net>

Documentation/00-INDEX

@@ -82,8 +82,6 @@ cgroup-v1/
 	- cgroups v1 features, including cpusets and memory controller.
 cgroup-v2.txt
 	- cgroups v2 features, including cpusets and memory controller.
-circular-buffers.txt
-	- how to make use of the existing circular buffer infrastructure
 clk.txt
 	- info on the common clock framework
 cma/

Documentation/core-api/index.rst

@@ -26,6 +26,7 @@ Core utilities
    genalloc
    errseq
    printk-formats
+   circular-buffers
 
 Interfaces for kernel debugging
 ===============================

Documentation/memory-barriers.txt

@@ -3083,7 +3083,7 @@ CIRCULAR BUFFERS
 Memory barriers can be used to implement circular buffering without the need
 of a lock to serialise the producer with the consumer.  See:
 
-	Documentation/circular-buffers.txt
+	Documentation/core-api/circular-buffers.rst
 
 for details.
 

Documentation/translations/ko_KR/memory-barriers.txt

@@ -3023,7 +3023,7 @@ smp_mb() 가 아니라 virt_mb() 를 사용해야 합니다.
 동기화에 락을 사용하지 않고 구현하는데에 사용될 수 있습니다.  더 자세한 내용을
 위해선 다음을 참고하세요:
 
-	Documentation/circular-buffers.txt
+	Documentation/core-api/circular-buffers.rst
 
 
 =========