debug: Add color to logs

Update log helpers to print errors in red and warnings in yellow.
It should make more easier to see errors and warnings when they printed
between greybus operation dump.

Signed-off-by: Alexandre Bailon <abailon@baylibre.com>

debug.h

@@ -22,6 +22,10 @@
 #include <stdio.h>
 #include <stdint.h>
 
+#define COLOR_RED	"\x1b[31m"
+#define COLOR_YELLOW	"\x1b[33m"
+#define COLOR_RESET	"\x1b[0m"
+
 enum log_level {
 	LL_ERROR = 0,
 	LL_WARNING,
@@ -39,10 +43,10 @@ enum log_level {
 	} while (0)
 
 #define pr_err(format, ...) \
-	ll_print(LL_ERROR, format, ##__VA_ARGS__)
+	ll_print(LL_ERROR, COLOR_RED format COLOR_RESET, ##__VA_ARGS__)
 
 #define pr_warn(format, ...) \
-	ll_print(LL_WARNING, format, ##__VA_ARGS__)
+	ll_print(LL_WARNING, COLOR_YELLOW format COLOR_RESET, ##__VA_ARGS__)
 
 #define pr_info(format, ...) \
 	ll_print(LL_INFO, format, ##__VA_ARGS__)