tty: fix kernel-doc for tty_{read,write}

tty: fix kernel-doc for tty_{read,write}

After commits a9cbbb80e3e7 (tty: avoid using vfs_iocb_iter_write() for
redirected console writes) and dd78b0c483e3 (tty: implement read_iter),
the tty_read and tty_write kernel-doc comments don't match the code:
 tty_io.c:931: warning: Function parameter or member 'iocb' not described in 'tty_read'
 tty_io.c:931: warning: Function parameter or member 'to' not described in 'tty_read'
 tty_io.c:931: warning: Excess function parameter 'file' description in 'tty_read'
 tty_io.c:931: warning: Excess function parameter 'buf' description in 'tty_read'
 tty_io.c:931: warning: Excess function parameter 'count' description in 'tty_read'
 tty_io.c:931: warning: Excess function parameter 'ppos' description in 'tty_read'
 tty_io.c:1115: warning: Function parameter or member 'iocb' not described in 'file_tty_write'
 tty_io.c:1115: warning: Function parameter or member 'from' not described in 'file_tty_write'
 tty_io.c:1115: warning: expecting prototype for tty_write(). Prototype was for file_tty_write() instead

Fix them to correspond the reality, i.e. the switch from read/write to
read_iter/write_iter.

Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210519072153.3859-3-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>