softmmu/memory: Pass ram_flags to qemu_ram_alloc_from_fd()

softmmu/memory: Pass ram_flags to qemu_ram_alloc_from_fd()

Let's pass in ram flags just like we do with qemu_ram_alloc_from_file(),
to clean up and prepare for more flags.

Simplify the documentation of passed ram flags: Looking at our
documentation of RAM_SHARED and RAM_PMEM is sufficient, no need to be
repetitive.

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Acked-by: Eduardo Habkost <ehabkost@redhat.com> for memory backend and machine core
Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20210510114328.21835-5-david@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>