regulator: da9121: Remove erroneous compatible from binding

Clean away information from a test that was included accidentally

Signed-off-by: Adam Ward <Adam.Ward.opensource@diasemi.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/530a626cee6bc12ff5b4ab16319ac7a1fac6e306.1638223185.git.Adam.Ward.opensource@diasemi.com


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