parisc: Enable power button switch and add option to disable it

Due to a mismatch of memory mapping for PA2.0 with PSW.W=0,
the power button was broken on 64-bit machines.
The mapping bug is now fixed in qemu, so re-enable the button again.

Additionally add option to completely disable the power
switch with:
    "-fw_cfg opt/power-button-enable,string=0"

Signed-off-by: Helge Deller <deller@gmx.de>
1 file changed