ec/google/chromeec: Add note before error message

When clearing events from the EC, an error is returned when we try
to clear an event that doesn't exist.  This is normal, but can
be distracting when trying to track down an error, so add a message
saying that the error is expected.

BUG=None
Test=Build Grunt with SMM debug enabled. See message before
"EC returned error result code 1".

Change-Id: Ib2e684e357e821c795de4b59658432c91a8d63fc
Signed-off-by: Martin Roth <martinroth@google.com>
Reviewed-on: https://review.coreboot.org/24914
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>

src/ec/google/chromeec/smihandler.c

@@ -53,6 +53,7 @@ static void clear_pending_events(void)
 	while (google_chromeec_get_event() != 0)
 		;
 
+	printk(BIOS_DEBUG,"Clearing pending EC events. Error code 1 is expected.\n");
 	while (google_chromeec_get_mkbp_event(&mkbp_event) == 0)
 		;
 }