serial: core: fix console problems on uart_close

Commit 761ed4a9 ('tty: serial_core: convert uart_close to use
tty_port_close') started setting the ttyport console flag for serial
drivers. This is causing crashes, hangs, or garbage output on several
platforms because the serial shutdown is skipped and IRQs are left
enabled.

Partially revert commit 761ed4a9 and drop reporting UART tty_ports
as a console leaving the console handling to the serial_core as it was
before.

Fixes: 761ed4a9 ("tty: serial_core: convert uart_close to use tty_port_close")
Reported-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reported-by: Mike Galbraith <umgwanakikbuti@gmail.com>
Reported-by: Mugunthan V N <mugunthanvnm@ti.com>
Cc: Peter Hurley <peter@hurleysoftware.com>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Alan Cox <alan@linux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jslaby@suse.com>
Cc: linux-serial@vger.kernel.org
Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>