mips: memory: Replace memory_region_init_ram with memory_region_allocate_system_memory

mips: memory: Replace memory_region_init_ram with memory_region_allocate_system_memory

Commit 0b183fc871:"memory: move mem_path handling to
memory_region_allocate_system_memory" split memory_region_init_ram and
memory_region_init_ram_from_file. Also it moved mem-path handling a step
up from memory_region_init_ram to memory_region_allocate_system_memory.

Therefore for any board that uses memory_region_init_ram directly,
-mem-path is not supported.

Fix this by replacing memory_region_init_ram with
memory_region_allocate_system_memory.

Signed-off-by: Dirk Mueller <[email protected]>
Message-Id: <CAL5wTH4-=HJUvwBu+2o6jGanJesJOyNf3sL8-5+d_-6C3cWBfA@mail.gmail.com>
Reviewed-by: Andreas Färber <[email protected]>
Acked-by: Leon Alrae <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>