serial: core: drop redundant TIOCGSERIAL memset

Since commit 5099d234 ("serial_core: switch to ->[sg]et_serial()")
the serial structure passed to uart_get_info() has already have been
cleared by the tty layer so drop the redundant memset.

Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20210407095208.31838-8-johan@kernel.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>