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.

Signed-off-by: Caleb Connolly <caleb.connolly@linaro.org>
4 files changed