sparc64: use memory_region_allocate_system_memory() only for '-m' specified RAM

sparc64: use memory_region_allocate_system_memory() only for '-m' specified RAM

memory_region_allocate_system_memory() was designed to be called for
allocating inital RAM. Using it mutiple times within one board is not
supported and could fail if -mem-path with non hugepage path is used.

Keep using memory_region_allocate_system_memory() only for initial
RAM and use memory_region_init_ram() for the rest fixed size regions.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Message-Id: <20191008113318.7012-2-imammedo@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>