common: spl: spl_fit.c: report an error on hash check fail

When the hash check fails on a loadable image, the SPL/TPL simply
jump to the next one. This commit changes this behaviour, when the
hash check fails on a loadable image, the function spl_load_simple_fit
stops and report an error.

Signed-off-by: Philippe Reynes <philippe.reynes@softathome.com>
Reviewed-by: Simon Glass <sjg@chromium.org>