slimbus: ngd: get drvdata from correct device

Get drvdata directly from parent instead of ngd dev, as ngd
dev can probe defer and previously set drvdata will become null.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20200417093618.7929-1-srinivas.kandagatla@linaro.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>