alpha: memory: Replace memory_region_init_ram with memory_region_allocate_system_memory

alpha: 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.

Cc: Richard Henderson <rth@twiddle.net>
Signed-off-by: Dirk Mueller <dmueller@suse.com>
Acked-by: Richard Henderson <rth@twiddle.net>
Message-id: CAL5wTH64_ykF17cw2T1Axq8P3vCWm=6WbUJ3qJrLF-u+-MmzUw@mail.gmail.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>