hw/arm/aspeed: Do not sysbus-map mmio flash region directly, use alias

hw/arm/aspeed: Do not sysbus-map mmio flash region directly, use alias

The flash mmio region is exposed as an AddressSpace.
AddressSpaces must not be sysbus-mapped, therefore map
the region using an alias.

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
[ clg : Fix DMA_FLASH_ADDR() ]
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Message-Id: <20210312182851.1922972-3-f4bug@amsat.org>
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Message-Id: <20210407171637.777743-6-clg@kaod.org>
Signed-off-by: Cédric Le Goater <clg@kaod.org>