pinctrl: qcom: stub support for special GPIOs

pinctrl: qcom: stub support for special GPIOs

Most platforms have a handful of "special" GPIOs, like the MMC
clock/data lanes, UFS reset, etc. These don't follow the usual naming
scheme of "gpioX" and also have unique capabilities and registers. We
can get away without supporting them all for now, but DT compatibility
is still an issue.

Add support for allowing these to be specified after the other pins, and
make all pinmux/pinconf calls for them nop.

Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Reviewed-by: Sumit Garg <sumit.garg@linaro.org>
Tested-by: Sumit Garg <sumit.garg@linaro.org> #qcs404
Signed-off-by: Caleb Connolly <caleb.connolly@linaro.org>