core/platform: Fallback to full_reboot if fast-reboot fails
core/platform: Fallback to full_reboot if fast-reboot fails

If fast reboot fails then we return to Linux with OPAL_SUCCESS.
Current Linux code thinks that request succedded and enters
infinite loop (see Linux pnv_restart() code).

This patch fixes above issue by return OPAL_UNSUPPORTED if fast
reboot fails.

Alternatively we can directly call full_reboot() itself. But I
think it makes sense to go back to Linux and report the failure.
And Linux falls back to normal reboot request.

Fixes: 10bbcd07 ("core/platform: Add an explicit fast-reboot type")
Cc: Oliver O'Halloran <3dfaff8fa6ae977f042064a112a6aac576279b9b@gmail.com>
Cc: Michael Ellerman <864f124608374e06e4da1fa5d2e47ed839b95411@ellerman.id.au>
Signed-off-by: Vasant Hegde <a6d753843573f7bfed5075c1e875b0be8007a0ab@linux.vnet.ibm.com>
Acked-by: Michael Ellerman <864f124608374e06e4da1fa5d2e47ed839b95411@ellerman.id.au>
Reviewed-by: Dan Horák <2591e5f46f28d303f9dc027d475a5c60d8dea17a@danny.cz>
Signed-off-by: Vasant Hegde <a6d753843573f7bfed5075c1e875b0be8007a0ab@linux.vnet.ibm.com>

qemu/skiboot,open-power/skiboot,shenki/skiboot,legoater/skiboot,legoater/skiboot,qemu/skiboot,legoater/skiboot,open-power/skiboot,qemu/skiboot,open-power/skiboot,shenki/skiboot,qemu/skiboot,legoater/skiboot,legoater/skiboot,open-power/skiboot,qemu/skiboot,shenki/skiboot,shenki/skiboot,open-power/skiboot,shenki/skiboot