hw/arm/highbank: don't make sysram 'nomigrate'

hw/arm/highbank: don't make sysram 'nomigrate'

Currently we use memory_region_init_ram_nomigrate() to create
the "highbank.sysram" memory region, and we don't manually
register it with vmstate_register_ram(). This currently
means that its contents are migrated but as a ram block
whose name is the empty string; in future it may mean they
are not migrated at all. Use memory_region_init_ram() instead.

Note that this is a cross-version migration compatibility
break for the "highbank" and "midway" machines.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 20180420124835.7268-2-peter.maydell@linaro.org