checkpatch.pl: Add 'printf' to logFunctions

Signed-off-by: Tom Rini <trini@ti.com>
diff --git a/tools/checkpatch.pl b/tools/checkpatch.pl
index 9f23901..896e2bc 100755
--- a/tools/checkpatch.pl
+++ b/tools/checkpatch.pl
@@ -273,6 +273,7 @@
 	WARN(?:_RATELIMIT|_ONCE|)|
 	panic|
 	debug|
+	printf|
 	MODULE_[A-Z_]+
 )};