Add checkpatch.pl to presubmit tests.

Change-Id: I235ea140f5f54dc8b22f1c69dcff5e99a34ff602
diff --git a/src/dlog.c b/src/dlog.c
index 322c054..1ce5566 100644
--- a/src/dlog.c
+++ b/src/dlog.c
@@ -53,9 +53,11 @@
 static size_t print_raw_string(const char *str)
 {
 	const char *c = str;
+
 	while (*c != '\0') {
 		arch_putchar(*c++);
 	}
+
 	return c - str;
 }