spl: fix debug prints for tiny printf

Tiny printf does not support %.*s and %lX. Since tiny printf should
be very common in SPL, replace these by %32s (for printing image
name) and %lx.

Signed-off-by: Simon Goldschmidt <simon.k.r.goldschmidt@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>