docs: filesystems: convert caching/fscache.txt to ReST format

- Add a SPDX header;
- Adjust document and section titles;
- Comment out text ToC for html/pdf output;
- Some whitespace fixes and new line breaks;
- Add table markups;
- Add it to filesystems/index.rst.
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/e33ec382a53cf10ffcbd802f6de3f384159cddba.1588021877.git.mchehab+huawei@kernel.orgSigned-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/filesystems/caching/index.rst

@@ -6,4 +6,5 @@ Filesystem Caching
 .. toctree::
    :maxdepth: 2
 
+   fscache
    object

fs/fscache/Kconfig

@@ -8,7 +8,7 @@ config FSCACHE
 	  Different sorts of caches can be plugged in, depending on the
 	  resources available.
 
-	  See Documentation/filesystems/caching/fscache.txt for more information.
+	  See Documentation/filesystems/caching/fscache.rst for more information.
 
 config FSCACHE_STATS
 	bool "Gather statistical information on local caching"
@@ -25,7 +25,7 @@ config FSCACHE_STATS
 	  between CPUs.  On the other hand, the stats are very useful for
 	  debugging purposes.  Saying 'Y' here is recommended.
 
-	  See Documentation/filesystems/caching/fscache.txt for more information.
+	  See Documentation/filesystems/caching/fscache.rst for more information.
 
 config FSCACHE_HISTOGRAM
 	bool "Gather latency information on local caching"
@@ -42,7 +42,7 @@ config FSCACHE_HISTOGRAM
 	  bouncing between CPUs.  On the other hand, the histogram may be
 	  useful for debugging purposes.  Saying 'N' here is recommended.
 
-	  See Documentation/filesystems/caching/fscache.txt for more information.
+	  See Documentation/filesystems/caching/fscache.rst for more information.
 
 config FSCACHE_DEBUG
 	bool "Debug FS-Cache"
@@ -52,7 +52,7 @@ config FSCACHE_DEBUG
 	  management module.  If this is set, the debugging output may be
 	  enabled by setting bits in /sys/modules/fscache/parameter/debug.
 
-	  See Documentation/filesystems/caching/fscache.txt for more information.
+	  See Documentation/filesystems/caching/fscache.rst for more information.
 
 config FSCACHE_OBJECT_LIST
 	bool "Maintain global object list for debugging purposes"