regulator: bd9576: fix regulator binfdings dt node names

Add regulator- prefix to allowed regulator node names. Prefix is expected
by the driver and the actual binding yaml description.

Signed-off-by: Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
Link: https://lore.kernel.org/r/3d92de2085f0c074929861a2f791bf4070920e83.1601885841.git.matti.vaittinen@fi.rohmeurope.com
Signed-off-by: Mark Brown <broonie@kernel.org>