sysreset: add Qualcomm PSHOLD reset driver

sysreset: add Qualcomm PSHOLD reset driver

Number of Qualcomm ARMv7 SoC-s did not use PSCI but rather used PSHOLD
(Qualcomm Power Supply Hold Reset) bit to trigger reset or poweroff.

Qualcomm IPQ40XX is one of them, so provide a simple sysreset driver based
on the upstream Linux one, it is DT compatible as well.

Signed-off-by: Robert Marko <robert.marko@sartura.hr>
Reviewed-by: Caleb Connolly <caleb.connolly@linaro.org>
Signed-off-by: Caleb Connolly <caleb.connolly@linaro.org>