kunit: test: Avoid cast warning when adding kfree() as an action

kunit: test: Avoid cast warning when adding kfree() as an action

In kunit_log_test() pass the kfree_wrapper() function to kunit_add_action()
instead of directly passing kfree().

This prevents a cast warning:

lib/kunit/kunit-test.c:565:25: warning: cast from 'void (*)(const void *)'
to 'kunit_action_t *' (aka 'void (*)(void *)') converts to incompatible
function type [-Wcast-function-type-strict]

   564		full_log = string_stream_get_string(test->log);
 > 565		kunit_add_action(test, (kunit_action_t *)kfree, full_log);

Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202311070041.kWVYx7YP-lkp@intel.com/
Fixes: 05e2006ce493 ("kunit: Use string_stream for test log")
Reviewed-by: David Gow <davidgow@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>