spl: Remove filename from spl_load_info

spl: Remove filename from spl_load_info

For filesystems, filename serves the same purpose as priv. However,
spl_load_fit_image also uses it to determine whether to use a DMA-aligned
buffer. This is beneficial for FAT, which uses a bounce-buffer if the
destination is not DMA-aligned. However, this is unnecessary now that
filesystems set bl_len to ARCH_DMA_MINALIGN instead. With this done, we can
remove filename entirely.

Signed-off-by: Sean Anderson <seanga2@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>