extcon: Add support for qcom SPMI PMIC USB id detection hardware

Some Qualcomm PMICs have a misc device that performs USB id pin
detection via an interrupt. When the interrupt triggers, we
should read the interrupt line to see if it has gone high or low.
If the interrupt is low then the ID pin is grounded, and if the
interrupt is high then the ID pin is being held high.

Cc: Roger Quadros <rogerq@ti.com>
Signed-off-by: Stephen Boyd <stephen.boyd@linaro.org>
[cw00.choi: Edited the driver description and added the author information]
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>