These functions are used in various drivers, including the latest
version of the 8250 driver. The latter causes the following build failure.
drivers/tty/serial/8250/8250_core.c: In function 'mem32be_serial_out':
drivers/tty/serial/8250/8250_core.c:456:2: error:
implicit declaration of function 'iowrite32be'
drivers/tty/serial/8250/8250_core.c: In function 'mem32be_serial_in':
drivers/tty/serial/8250/8250_core.c:462:2: error:
implicit declaration of function 'ioread32be'