hw/core/loader.c: Remove load_image()

hw/core/loader.c: Remove load_image()

The load_image() function is now no longer used anywhere, so
we can remove it completely. (Use load_image_size() or
g_file_get_contents() instead.)

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-id: 20181130151712.2312-10-peter.maydell@linaro.org