pm8921: Add support for USB PMIC ID interrupt

PHY OTG comparators can be disabled for maximum power savings.  PHY
can not generate ID interrupt in this case.  As USB id line is routed
to PM8921 on MSM8960, depend on PM8921 for ID interrupt.

Change-Id: If375274d30235f7e950e284fabc72a4d6b5bc269
Signed-off-by: Vijayavardhan <vvreddy@codeaurora.org>
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>
[sboyd: only take the pm8921 part and reword subject]
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>