arm/dt: 8974: Add power collapse counter device

The power collapse counter driver is a debug utility that keeps track of
power collapse events for each core. Adding this driver helps debug the
state of power collapse on every core.

Change-Id: I7165a5f61bd0c83f0ce76f8c9c2bdd6be3a44c76
Signed-off-by: Mahesh Sivasubramanian <msivasub@codeaurora.org>