kunit_tool relies on the UML console outputting printk() output to the
tty in order to get results. Since the default console driver could
change, pass 'console=tty' to the kernel.

This is triggered by a change[1] to use ttynull as a fallback console
driver which -- by chance or by design -- seems to have changed the
default console output on UML, breaking kunit_tool. While this may be
fixed, we should be less fragile to such changes in the default.

[1]:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=757055ae8dedf5333af17b3b5b4b70ba9bc9da4eSigned-off-by: David Gow <davidgow@google.com>
Fixes: 757055ae ("init/console: Use ttynull as a fallback when there is no console")
Reported-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Tested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Brendan Higgins <brendanhiggins@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>