Input: add powerkey driver for HISI 65xx SoC

This driver provides a input driver for the power button on the
HiSi 65xx SoC for boards like HiKey.

This driver was originally by Zhiliang Xue <xuezhiliang@huawei.com>
then basically rewritten by Jorge, but preserving the original
module author credits.

Signed-off-by: Jorge Ramirez-Ortiz <jorge.ramirez-ortiz@linaro.org>
[jstultz: Reworked commit message, folded in other fixes/cleanups
from Jorge, implemented some larger cleanups suggested by DmitryT]
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/misc/Makefile

@@ -35,6 +35,7 @@ obj-$(CONFIG_INPUT_DRV2667_HAPTICS)	+= drv2667.o
 obj-$(CONFIG_INPUT_GP2A)		+= gp2ap002a00f.o
 obj-$(CONFIG_INPUT_GPIO_BEEPER)		+= gpio-beeper.o
 obj-$(CONFIG_INPUT_GPIO_TILT_POLLED)	+= gpio_tilt_polled.o
+obj-$(CONFIG_INPUT_HISI_POWERKEY)	+= hisi_powerkey.o
 obj-$(CONFIG_HP_SDC_RTC)		+= hp_sdc_rtc.o
 obj-$(CONFIG_INPUT_IMS_PCU)		+= ims-pcu.o
 obj-$(CONFIG_INPUT_IXP4XX_BEEPER)	+= ixp4xx-beeper.o