gpio: qcom_pmic: drop gpio-count property

This property is not part of the dt bindings and all boards use the new
gpio-ranges property instead. Drop support for this.

Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Reviewed-by: Sumit Garg <sumit.garg@linaro.org>
Tested-by: Sumit Garg <sumit.garg@linaro.org>
Signed-off-by: Caleb Connolly <caleb.connolly@linaro.org>