[otbnsim] Run tests through mypy

Signed-off-by: Philipp Wagner <phw@lowrisc.org>

hw/ip/otbn/dv/otbnsim/Makefile

diff --git a/hw/ip/otbn/dv/otbnsim/Makefile b/hw/ip/otbn/dv/otbnsim/Makefile
index b0c11d6..78b5104 100644
--- a/hw/ip/otbn/dv/otbnsim/Makefile
+++ b/hw/ip/otbn/dv/otbnsim/Makefile
@@ -14,7 +14,7 @@
 	mkdir -p $@
 
 py-scripts := standalone.py stepped.py
-py-files   := $(wildcard *.py sim/*.py)
+py-files   := $(wildcard *.py sim/*.py test/*.py)
 py-libs    := $(filter-out $(py-scripts),$(py-files))
 
 lint-stamps := $(foreach scr,$(py-scripts),$(build-dir)/$(scr).stamp)