regulator: qpnp-regulator: Add snapshot of qpnp-regulator

Add snapshot of qpnp-regulator from kernel 4.9 as of commit

7262d3811169("Merge "usb: gadget: handle usb connection events").

While at it, add support for debugfs node for qpnp-regulator.

Change-Id: Ie493446009c708339af93e9d81af47b8538b8c52
Signed-off-by: Kavya Nunna <knunna@codeaurora.org>