MIPS: AR7: ensure the port type's FCR value is used

Since commit aef9a7bd ("serial/uart/8250: Add tunable RX interrupt
trigger I/F of FIFO buffers"), the port's default FCR value isn't used
in serial8250_do_set_termios anymore, but copied over once in
serial8250_config_port and then modified as needed.

Unfortunately, serial8250_config_port will never be called if the port
is shared between kernel and userspace, and the port's flag doesn't have
UPF_BOOT_AUTOCONF, which would trigger a serial8250_config_port as well.

This causes garbled output from userspace:

[    5.220000] random: procd urandom read with 49 bits of entropy available
ers
   [kee

Fix this by forcing it to be configured on boot, resulting in the
expected output:

[    5.250000] random: procd urandom read with 50 bits of entropy available
Press the [f] key and hit [enter] to enter failsafe mode
Press the [1], [2], [3] or [4] key and hit [enter] to select the debug level

Fixes: aef9a7bd ("serial/uart/8250: Add tunable RX interrupt trigger I/F of FIFO buffers")
Signed-off-by: Jonas Gorski <jonas.gorski@gmail.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@hitachi.com>
Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: Nicolas Schichan <nschichan@freebox.fr>
Cc: linux-mips@linux-mips.org
Cc: linux-serial@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/17544/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>