tty: amba-pl011: convert accessor functions to take uart_amba_port

Convert the new accessor functions to take the uart_amba_port instead
of the port base address.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>