ASoC: da7219: Correct IRQ level in DT binding example

Current DT binding documentation shows an example where the IRQ
for the device is chosen to be ACTIVE_HIGH. This is incorrect as
the device only supports ACTIVE_LOW, so this commit fixes that
discrepancy.

Signed-off-by: Adam Thomson <Adam.Thomson.Opensource@diasemi.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Mark Brown <broonie@kernel.org>