console: Add a function to read a line of the output / eof

When recording the console output for testing it is useful to be able to
read the output a line at a time to check that the output is correct. Also
we need to check that we get to the end of the output.

Add a console function to return the next line and another to see how must
data is left.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/common/console.c b/common/console.c
index 168ba60..7681da1 100644
--- a/common/console.c
+++ b/common/console.c
@@ -621,6 +621,17 @@
 	console_record_reset();
 	gd->flags |= GD_FLG_RECORD;
 }
+
+int console_record_readline(char *str, int maxlen)
+{
+	return membuff_readline(&gd->console_out, str, maxlen, ' ');
+}
+
+int console_record_avail(void)
+{
+	return membuff_avail(&gd->console_out);
+}
+
 #endif
 
 /* test if ctrl-c was pressed */