regmap: debugfs: Add back in erroneously removed initialisation of ret

Fixes: 94cc89eb ("regmap: debugfs: Fix handling of name string for debugfs init delays")
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Link: https://lore.kernel.org/r/20200918112002.15216-1-ckeepax@opensource.cirrus.com


Signed-off-by: Mark Brown <broonie@kernel.org>