genpd: Makefile: build imx

The imx genpd was missed to be built out, add it in Makefile
Signed-off-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/genpd/Makefile

@@ -3,6 +3,7 @@ obj-y					+= actions/
 obj-y					+= amlogic/
 obj-y					+= apple/
 obj-y					+= bcm/
+obj-y					+= imx/
 obj-y					+= mediatek/
 obj-y					+= qcom/
 obj-y					+= renesas/