ASoC: tlv320adcx140: Remove undocumented property

ASoC: tlv320adcx140: Remove undocumented property

Remove undocumented and unneeded ti,use-internal-reg from the example as
it was an artifact from initial development.  The code does not query
for this property and as the document indicates if areg-supply is
undefined then the internal regulator is used.

Fixes: 302c0b7490cd ("dt-bindings: sound: Add TLV320ADCx140 dt
bindings")
Signed-off-by: Dan Murphy <dmurphy@ti.com>
CC: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20200327162432.17067-1-dmurphy@ti.com
Signed-off-by: Mark Brown <broonie@kernel.org>