button: qcom-pmic: introduce Qualcomm PMIC button driver

Qualcomm PMICs include a "pon" function which handles two buttons, the
power button and "resin" button (usually volume down). Introduce a new
driver following upstream Linux DT to enable these and map them to Enter
and Down respectively to enable use in boot menus.

Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Reviewed-by: Sumit Garg <sumit.garg@linaro.org>
Tested-by: Sumit Garg <sumit.garg@linaro.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Caleb Connolly <caleb.connolly@linaro.org>
diff --git a/drivers/button/Makefile b/drivers/button/Makefile
index bbd18af..6855508 100644
--- a/drivers/button/Makefile
+++ b/drivers/button/Makefile
@@ -5,3 +5,4 @@
 obj-$(CONFIG_BUTTON) += button-uclass.o
 obj-$(CONFIG_BUTTON_ADC) += button-adc.o
 obj-$(CONFIG_BUTTON_GPIO) += button-gpio.o
+obj-$(CONFIG_BUTTON_QCOM_PMIC) += button-qcom-pmic.o
\ No newline at end of file