test: Rename optee test-file

This has nothing to do with commands anymore, so rename the file.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/test/optee/Makefile b/test/optee/Makefile
index 8793fd7..ec56750 100644
--- a/test/optee/Makefile
+++ b/test/optee/Makefile
@@ -3,7 +3,7 @@
 # Copyright (C) 2019, Theobroma Systems Design und Consulting GmbH
 
 # Test files
-obj-y += cmd_ut_optee.o
+obj-y += optee.o
 
 DTC_FLAGS += -@
 
diff --git a/test/optee/cmd_ut_optee.c b/test/optee/optee.c
similarity index 100%
rename from test/optee/cmd_ut_optee.c
rename to test/optee/optee.c