msm: pil: Add name and state sysfs nodes

Userspace wants to know when a peripheral is online and if it has
rebooted. Add support for two sysfs nodes, name and state, to
notify userspace when such events happen.

The intent is for userspace to poll() the state node waiting for
the state to change. Once the peripheral goes offline, poll()
should return and userspace knows that the peripheral has booted
again.

Add a name node so that userspace can easily iterate over all
devices in /sys/bus/pil/devices/ to know what peripheral is
in what state.

Change-Id: I33c9dd42419b2e960d58dd2cd04cd82ddc1f5d60
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>