scripts: better handling of printf: stdout/stderr

in some cases, messages that should be considered errors
or warnings, were being written to the standard output,
rather than written as error messages.

also: one or two printf statements should specifically
avoid printing errors (to any file); in these cases,
stdout has been redirected to /dev/null

Signed-off-by: Leah Rowe <leah@libreboot.org>

script/update/blobs/mrc

@@ -62,11 +62,11 @@ check_existing()
 {
 	[ -f "${_mrc_complete}" ] || \
 		return 0
-	printf 'found existing mrc.bin\n'
+	printf "found existing mrc.bin\n" 1>&2
 	[ "$(sha512sum "${_mrc_complete}" | awk '{print $1}')" \
 	    = "${_mrc_complete_hash}" ] && \
 		return 1
-	printf 'hashes did not match, starting over\n'
+	printf "hashes did not match, starting over\n" 1>&2
 }
 
 build_dependencies()