serial: altera-uart: fix NULL device in log message

Add device pointer to port->dev.

Before:

"(NULL device *): ttyAL0 at MMIO 0x2020 (irq = 6, base_baud = 3125000)
is a Altera UART"

After:
"altera_uart 2020.serial: ttyAL0 at MMIO 0x2020 (irq = 6, base_baud = 3125000)
is a Altera UART"

Signed-off-by: Ley Foon Tan <lftan@altera.com>
Acked-by: Tobias Klauser <tklauser@distanz.ch>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>