power: add IIO as observable by powerd

powerd will want to listen for IIO proximity sensors and this is
a necessary prerequisite to make that work.

TEST=manual on Nautilus
BUG=b:74586744

Change-Id: I07c9def21aba302a033a0aa4f04f09c292cc3005
Signed-off-by: Enrico Granata <egranata@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1148687
Reviewed-by: Dan Erat <derat@chromium.org>
(cherry picked from commit 0ac68c59d7e402c309515655fb161ee81960f3f4)
Reviewed-on: https://chromium-review.googlesource.com/1154708
Commit-Queue: Jongpil Jung <jongpil19.jung@samsung.corp-partner.google.com>
Tested-by: Jongpil Jung <jongpil19.jung@samsung.corp-partner.google.com>
diff --git a/power_manager/udev/94-powerd-late.rules b/power_manager/udev/94-powerd-late.rules
index 55d158f..60859c7 100644
--- a/power_manager/udev/94-powerd-late.rules
+++ b/power_manager/udev/94-powerd-late.rules
@@ -12,6 +12,7 @@
 # The "powerd" tag needs to be added to subsystems which powerd observes.
 SUBSYSTEM=="drm",          TAG+="powerd"
 SUBSYSTEM=="i2c-dev",      TAG+="powerd"
+SUBSYSTEM=="iio",          TAG+="powerd"
 SUBSYSTEM=="input",        TAG+="powerd"
 SUBSYSTEM=="leds",         TAG+="powerd"
 SUBSYSTEM=="net",          TAG+="powerd"