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>

test/py/u_boot_console_sandbox.py

@@ -44,6 +44,7 @@ class ConsoleSandbox(ConsoleBase):
             cmd += ['gdbserver', self.config.gdbserver]
         cmd += [
             self.config.build_dir + '/u-boot',
+            '-v',
             '-d',
             self.config.build_dir + '/arch/sandbox/dts/test.dtb'
         ]