misc: fs_loader: Fix compiler warning

Fix compiler warning

drivers/misc/fs_loader.c:193:9: warning: format ‘%d’ expects
argument of type ‘int’, but argument 5 has type ‘size_t
{aka long unsigned int}’ [-Wformat=]

Signed-off-by: Keerthy <j-keerthy@ti.com>
Reviewed-by: Simon Glass <sjg@chromium.org>