Use Android log system in helpers.c.

This code might be loaded by a daemonized process now, so the existing
logging to stderr goes nowhere. It's better to use the Android logger.

Change-Id: I19f088b8f049f07c9c6839038d2971fad1a0e852
Reviewed-on: https://chromium-review.googlesource.com/971360
Commit-Ready: Alistair Strachan <astrachan@google.com>
Tested-by: Alistair Strachan <astrachan@google.com>
Reviewed-by: Alistair Strachan <astrachan@google.com>
Reviewed-by: Gurchetan Singh <gurchetansingh@chromium.org>
diff --git a/drv.h b/drv.h
index 18653e5..2271a9f 100644
--- a/drv.h
+++ b/drv.h
@@ -164,6 +164,14 @@
 
 uint32_t drv_num_buffers_per_bo(struct bo *bo);
 
+#define drv_log(format, ...)                                                                       \
+	do {                                                                                       \
+		drv_log_prefix("minigbm", __FILE__, __LINE__, format, ##__VA_ARGS__);              \
+	} while (0)
+
+__attribute__((format(printf, 4, 5))) void drv_log_prefix(const char *prefix, const char *file,
+							  int line, const char *format, ...);
+
 #ifdef __cplusplus
 }
 #endif