dt-bindings: iio: adf4377: add adf4378 support

dt-bindings: iio: adf4377: add adf4378 support

The adf4378 provides only one output channel. Therefore there is only
one gpio available to enable the output. Reflect that into the bindings
using property conditions.

Add product link for the adf4378.

Signed-off-by: Antoniu Miclaus <antoniu.miclaus@analog.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://patch.msgid.link/20240729095047.25040-2-antoniu.miclaus@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>