test: Fix mulptiplex_log typo

Fix a typo in a comment.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/test/py/u_boot_console_base.py b/test/py/u_boot_console_base.py
index aebe0da..d8d0bdf 100644
--- a/test/py/u_boot_console_base.py
+++ b/test/py/u_boot_console_base.py
@@ -113,7 +113,7 @@
         Can only usefully be called by sub-classes.
 
         Args:
-            log: A mulptiplex_log.Logfile object, to which the U-Boot output
+            log: A multiplexed_log.Logfile object, to which the U-Boot output
                 will be logged.
             config: A configuration data structure, as built by conftest.py.
             max_fifo_fill: The maximum number of characters to send to U-Boot