When shutting down the adapter, SLOF writes 0 to the Event Ring Segment
Table Base Address Register (ERSTBA) but does not reset the Event Ring
Segment Table Size Register (ERSTSZ) which makes QEMU do DMA access
at zero address which fails in unassigned_mem_accepts.
This resets ERSTSZ right before resetting ERSTBA so these 2 registers
can stay in sync.
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Reviewed-by: Nikunj A Dadhania <nikunj@linux.vnet.ibm.com>
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