bus: mvebu-mbus: Provide stub function for mvebu_mbus_get_io_win_info()

This patch provides a stub function for mvebu_mbus_get_io_win_info(),
which will be used for all non-Orion (ARM32 MVEBU) platforms for
compile test coverage.

On such platforms this function will return an error so that drivers
might detect a potential problem.

Signed-off-by: Stefan Roese <sr@denx.de>
Acked-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Marcin Wojtas <mw@semihalf.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Andrew Lunn <andrew@lunn.ch>
Cc: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>