scsi: docs: convert st.txt to ReST

Link: https://lore.kernel.org/r/6b2ddb36983e81e7028de6e5fd0c643c2fb4c6c9.1583136624.git.mchehab+huawei@kernel.org
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/st.c

@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0-only
 /*
    SCSI Tape Driver for Linux version 1.1 and newer. See the accompanying
-   file Documentation/scsi/st.txt for more information.
+   file Documentation/scsi/st.rst for more information.
 
    History:
    Rewritten from Dwayne Forsyth's SCSI tape driver by Kai Makisara.