docs: core-api: add cachetlb documentation

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

Documentation/00-INDEX

@@ -76,8 +76,6 @@ bus-devices/
 	- directory with info on TI GPMC (General Purpose Memory Controller)
 bus-virt-phys-mapping.txt
 	- how to access I/O mapped memory from within device drivers.
-cachetlb.txt
-	- describes the cache/TLB flushing interfaces Linux uses.
 cdrom/
 	- directory with information on the CD-ROM drivers that Linux has.
 cgroup-v1/

Documentation/core-api/index.rst

@@ -14,6 +14,7 @@ Core utilities
    kernel-api
    assoc_array
    atomic_ops
+   cachetlb
    refcount-vs-atomic
    cpu_hotplug
    idr

Documentation/memory-barriers.txt

@@ -2903,7 +2903,7 @@ is discarded from the CPU's cache and reloaded.  To deal with this, the
 appropriate part of the kernel must invalidate the overlapping bits of the
 cache on each CPU.
 
-See Documentation/cachetlb.txt for more information on cache management.
+See Documentation/core-api/cachetlb.rst for more information on cache management.
 
 
 CACHE COHERENCY VS MMIO

Documentation/translations/ko_KR/memory-barriers.txt

@@ -2846,7 +2846,7 @@ CPU 의 캐시에서 RAM 으로 쓰여지는 더티 캐시 라인에 의해 덮
 문제를 해결하기 위해선, 커널의 적절한 부분에서 각 CPU 의 캐시 안의 문제가 되는
 비트들을 무효화 시켜야 합니다.
 
-캐시 관리에 대한 더 많은 정보를 위해선 Documentation/cachetlb.txt 를
+캐시 관리에 대한 더 많은 정보를 위해선 Documentation/core-api/cachetlb.rst 를
 참고하세요.