test/py: pass -v option when executing sandbox

This shows more output, such as the internal output generated by the unit
test ("ut") command, which makes it easier to debug issues.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/test/py/u_boot_console_sandbox.py b/test/py/u_boot_console_sandbox.py
index 3de0fe4..04654ae 100644
--- a/test/py/u_boot_console_sandbox.py
+++ b/test/py/u_boot_console_sandbox.py
@@ -44,6 +44,7 @@
             cmd += ['gdbserver', self.config.gdbserver]
         cmd += [
             self.config.build_dir + '/u-boot',
+            '-v',
             '-d',
             self.config.build_dir + '/arch/sandbox/dts/test.dtb'
         ]