log: Add helpers for common log levels

At present to output a log message you need something like:

   log(UCLASS_SPI, LOCL_INFO, "message1");
   log(UCLASS_SPI, LOCL_INFO, "message2");

but many files use the same category throughout. Also it is helpful to
shorten the length of log names, providing helpers for common logging
levels. Add some macros so that it is possible to do:

   (top of file, before #includes)
   #define LOG_CATEGORY UCLASS_SPI

   (later in the file)
   log_info("message1");
   log_debug("message2");
   log_err("message3");

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/include/log.h b/include/log.h
index 75ff1e1..1d936ec 100644
--- a/include/log.h
+++ b/include/log.h
@@ -88,8 +88,22 @@
  */
 #if CONFIG_IS_ENABLED(LOG)
 #define _LOG_MAX_LEVEL CONFIG_VAL(LOG_MAX_LEVEL)
+#define log_err(_fmt...)	log(LOG_CATEGORY, LOGL_ERR, ##_fmt)
+#define log_warning(_fmt...)	log(LOG_CATEGORY, LOGL_WARNING, ##_fmt)
+#define log_notice(_fmt...)	log(LOG_CATEGORY, LOGL_NOTICE, ##_fmt)
+#define log_info(_fmt...)	log(LOG_CATEGORY, LOGL_INFO, ##_fmt)
+#define log_debug(_fmt...)	log(LOG_CATEGORY, LOGL_DEBUG, ##_fmt)
+#define log_content(_fmt...)	log(LOG_CATEGORY, LOGL_DEBUG_CONTENT, ##_fmt)
+#define log_io(_fmt...)		log(LOG_CATEGORY, LOGL_DEBUG_IO, ##_fmt)
 #else
 #define _LOG_MAX_LEVEL LOGL_INFO
+#define log_err(_fmt...)
+#define log_warning(_fmt...)
+#define log_notice(_fmt...)
+#define log_info(_fmt...)
+#define log_debug(_fmt...)
+#define log_content(_fmt...)
+#define log_io(_fmt...)
 #endif
 
 /* Emit a log record if the level is less that the maximum */