regulator: act8865: set correct number of regulators in pdata

act8865_pdata_from_dt() populates the array pdata->regulators with all
the regulators and then assigns the field init_data only for the ones
actually found in the DT.

The patch changes the value assigned to pdata->num_regulators to match
the size of the array.

Signed-off-by: Beniamino Galvani <b.galvani@gmail.com>
Tested-by: Wenyou Yang <wenyou.yang@atmel.com>
Reviewed-by: Axel Lin <axel.lin@ingics.com>
Signed-off-by: Mark Brown <broonie@linaro.org>