tty: fix up and plug in tty_ioctl kernel-doc

The ioctl helpers are well documented, except they are not plugged in
the Documentation. So fix up the minor issues in the kernel-doc and plug
it in.

The minor issues include:
* bad \t on every line (sphinx misinterprets the description otherwise)
* missing colon after Return
* superfluous \n after the comment
* make some struct members and constants a hyperlink
* and so on

Perhaps better to use --word-diff if one wants to see the "real"
changes.
Signed-off-by: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20230919085156.1578-9-jirislaby@kernel.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/driver-api/tty/index.rst

@@ -36,6 +36,7 @@ In-detail description of the named TTY structures is in separate documents:
    tty_struct
    tty_ldisc
    tty_buffer
+   tty_ioctl
    tty_internals
 
 Writing TTY Driver

Documentation/driver-api/tty/tty_ioctl.rst

+.. SPDX-License-Identifier: GPL-2.0
+
+=================
+TTY IOCTL Helpers
+=================
+
+.. kernel-doc:: drivers/tty/tty_ioctl.c