[ARM] 3158/1: SharpSL: Add PM device driver for the SL-C7x0 machines.

Patch from Richard Purdie

Add a SharpSL PM device driver for the SL-C7x0 machines.

Signed-off-by: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>