regulator: max1586: zero-initialize regulator match table array

The struct of_regulator_match rmatch[] is declared as a non-static local
variable so the structure members are not auto-initialized.

Initialize the array at declaration time to avoid the structure members
values to be indeterminate and have sane defaults instead.

Signed-off-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
Signed-off-by: Mark Brown <broonie@kernel.org>