regulator: bd9576: Fix return from bd957x_probe()

The probe() function returns an uninitialized variable in the success
path.  There is no need for the "err" variable at all, just delete it.

Fixes: b014e9fa

 ("regulator: Support ROHM BD9576MUF and BD9573MUF")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
Link: https://lore.kernel.org/r/YEsbfLJfEWtnRpoU@mwanda
Signed-off-by: Mark Brown <broonie@kernel.org>