pmic: Convert pm8916 driver to a generic Qcom PMIC driver

Since both pm8916.c and pm8916_gpio.c are already supporting multiple
Qcom SoCs, it makes sense to rename these drivers to pmic_qcom.c and
qcom_pmic_gpio.c respectively. Also, these driver can be extended to
support additional functionality if required for other Qcom SoCs.

Along with this import latest DT binding: qcom,spmi-pmic.txt from Linux
kernel and thereby remove pm8916.txt.

Signed-off-by: Sumit Garg <sumit.garg@linaro.org>
diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 7e4c357..c949f9d 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -303,14 +303,14 @@
 	  legacy GPIO interface. Several subcommands are provided which mirror
 	  the standard 'gpio' command. It should use that instead.
 
-config PM8916_GPIO
-	bool "Qualcomm PM8916 PMIC GPIO/keypad driver"
-	depends on DM_GPIO && PMIC_PM8916
+config QCOM_PMIC_GPIO
+	bool "Qualcomm generic PMIC GPIO/keypad driver"
+	depends on DM_GPIO && PMIC_QCOM
 	help
 	  Support for GPIO pins and power/reset buttons found on
-	  Qualcomm PM8916 PMIC.
+	  Qualcomm SoCs PMIC.
 	  Default name for GPIO bank is "pm8916".
-	  Power and reset buttons are placed in "pm8916_key" bank and
+	  Power and reset buttons are placed in "pwkey_qcom" bank and
           have gpio numbers 0 and 1 respectively.
 
 config PCF8575_GPIO