dt-bindings: i2c: nomadik: Drop unused voltage supply from example

This drops the pointless v-i2c-supply from the Nomadik I2C
example. This is a leftover from before the use of power
domains when the power domain voltage was attached to a
regulator.

The unused property in the device trees will be removed
in a separate patch.

Reported-by: Rob Herring <robh@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Wolfram Sang <wsa@kernel.org>