frv: add io{read,write}{16,32}be functions

frv: add io{read,write}{16,32}be functions

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'

Cc: Kevin Cernekee <[email protected]>
Acked-by: Greg Kroah-Hartman <[email protected]>
Fixes: c627f2ceb692 ("serial: 8250: Add support for big-endian MMIO
	accesses")
Signed-off-by: Guenter Roeck <[email protected]>
Signed-off-by: Rob Herring <[email protected]>