Add the capability for the PXA architecture to poweroff.

As there is no true poweroff, ie. the power regulator is not available
for shut off from the core, the poweroff puts the SoC into a deep sleep
mode (mode 7), where almost no current is sunk.

Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

Use PXA register RCSR to detect which is the reset cause.  When
triggering a reset, clear the former reset source first.

Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

The core support was brought by Marc and Sascha.
The cache choice was fixed by Luotao Fu.
Some gpio and devices addons were provided by Robert.

Signed-off-by: Luotao Fu <l.fu@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>