Documentation: filesystems: convert vfat.txt to RST

Converts vfat.txt to the reStructuredText format, improving presentation
without changing the underlying content.

Signed-off-by: Daniel W. S. Almeida <dwlsalmeida@gmail.com>
-----------------------------------------------------------
Changes in v3:
Removed unnecessary markup.
Removed section "BUG REPORTS" as recommended by the maintainer.

Changes in v2:
Refactored long lines as pointed out by Jonathan
Copied the maintainer
Updated the reference in the MAINTAINERS file for vfat

I did not move this into admin-guide, waiting on what the
maintainer has to say about this and also about old sections
in the text, if any.

Link: https://lore.kernel.org/r/20191223010030.434902-1-dwlsalmeida@gmail.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
diff --git a/MAINTAINERS b/MAINTAINERS
index cc0a4a8..1df6007 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -17356,7 +17356,7 @@
 VFAT/FAT/MSDOS FILESYSTEM
 M:	OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
 S:	Maintained
-F:	Documentation/filesystems/vfat.txt
+F:	Documentation/filesystems/vfat.rst
 F:	fs/fat/
 
 VFIO DRIVER