char/mwave: drop it

When I tried to clean up the driver a bit, Arnd noted:
> According to thinkwiki.de, the 3780i modem was only used in a
> couple of Thinkpad models that are now over 25 years old, using
> Pentium II processors, and they all have a physical RS232 port
> that can be used to connect an external modem instead.
>
> Maybe we can just retire this driver?

So instead of the clean up, drop the driver altogether.

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
Suggested-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/all/b8834e5d-fdde-4b1a-8757-288dddc507a9@app.fastmail.com/
Link: https://patch.msgid.link/20251124103952.995229-1-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/userspace-api/ioctl/ioctl-number.rst

@@ -397,7 +397,6 @@ Code  Seq#    Include File                                             Comments
 0xCD  01     linux/reiserfs_fs.h                                       Dead since 6.13
 0xCE  01-02  uapi/linux/cxl_mem.h                                      Compute Express Link Memory Devices
 0xCF  02     fs/smb/client/cifs_ioctl.h
-0xDB  00-0F  drivers/char/mwave/mwavepub.h
 0xDD  00-3F                                                            ZFCP device driver see drivers/s390/scsi/
                                                                        <mailto:aherrman@de.ibm.com>
 0xE5  00-3F  linux/fuse.h