test: cmd: setexpr: Fix a typo

SETEXPR_TEST is for a new setexpr test, not mem.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/test/cmd/setexpr.c b/test/cmd/setexpr.c
index 27113c0..c537e89 100644
--- a/test/cmd/setexpr.c
+++ b/test/cmd/setexpr.c
@@ -15,7 +15,7 @@
 
 #define BUF_SIZE	0x100
 
-/* Declare a new mem test */
+/* Declare a new setexpr test */
 #define SETEXPR_TEST(_name, _flags)	UNIT_TEST(_name, _flags, setexpr_test)
 
 /* Test 'setexpr' command with simply setting integers */