binman: Reset missing bintools after testing

For tests which fake bintools being missing, we need to reset the list
afterwards, to ensure that future tests do not also see the bintools as
missing.

Reset the list when processing is complete.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Neha Malcom Francis <n-francis@ti.com>
diff --git a/tools/binman/control.py b/tools/binman/control.py
index c6d3205..2f00279 100644
--- a/tools/binman/control.py
+++ b/tools/binman/control.py
@@ -858,6 +858,8 @@
                 data = state.GetFdtForEtype('u-boot-dtb').GetContents()
                 elf.UpdateFile(*elf_params, data)
 
+            bintool.Bintool.set_missing_list(None)
+
             # This can only be True if -M is provided, since otherwise binman
             # would have raised an error already
             if invalid: