package_deb: When searching for E:, anchor expression

If we don't do this it will match on expressions like "NOTE:" which
are not fatal errors.

(From OE-Core rev: 8f4e160ce0b0c755545d62b06db14decd45b9f1e)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/package_deb.bbclass

@@ -187,7 +187,7 @@ deb_log_check() {
 	lf_path="$2"
 
 	lf_txt="`cat $lf_path`"
-	for keyword_die in "E:"
+	for keyword_die in "^E:"
 	do
 		if (echo "$lf_txt" | grep -v log_check | grep "$keyword_die") >/dev/null 2>&1
 		then