softmmu/physmem: Fixup qemu_ram_block_from_host() documentation

softmmu/physmem: Fixup qemu_ram_block_from_host() documentation

Let's fixup the documentation (e.g., removing traces of the ram_addr
parameter that no longer exists) and move it to the header file while at
it.

Message-ID: <20230926185738.277351-4-david@redhat.com>
Suggested-by: Igor Mammedov <imammedo@redhat.com>
Acked-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>