When detaching contexts, we may still have interrupts in the system
which are yet to be delivered to any CPU and be acked in the PSL.
This can result in a subsequent unrelated process getting an spurious
IRQ or an interrupt for a non-existent context.

This polls the PSL to ensure that the PSL is clear of IRQs for the
detached context, before removing the context from the idr.
Signed-off-by: Michael Neuling <mikey@neuling.org>
Tested-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>
Acked-by: Ian Munsie <imunsie@au1.ibm.com>
Tested-by: Vaibhav Jain <vaibhav@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>