misc: pti: Fix documentation for bit-rotted function pti_tty_driver_write()

misc: pti: Fix documentation for bit-rotted function pti_tty_driver_write()

The API has moved on since the original function header was
authored.  This changes brings the function's documentation
back into line with reality, complete descriptions of the
latest arguments to be used.

Squashes the following W=1 kernel build warnings:

 drivers/misc/pti.c:510: warning: Function parameter or member 'tty' not described in 'pti_tty_driver_wr
 drivers/misc/pti.c:510: warning: Function parameter or member 'buf' not described in 'pti_tty_driver_wr
 drivers/misc/pti.c:510: warning: Excess function parameter 'filp' description in 'pti_tty_driver_write'
 drivers/misc/pti.c:510: warning: Excess function parameter 'data' description in 'pti_tty_driver_write'

Cc: J Freyensee <james_p_freyensee@linux.intel.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20200626130525.389469-11-lee.jones@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>