hw/block/nvme: zero out zones on reset

hw/block/nvme: zero out zones on reset

The zoned command set specification states that "All logical blocks in a
zone *shall* be marked as deallocated when [the zone is reset]". Since
the device guarantees 0x00 to be read from deallocated blocks we have to
issue a pwrite_zeroes since we cannot be sure that a discard will do
anything. But typically, this will be achieved with an efficient
unmap/discard operation.

Signed-off-by: Klaus Jensen <k.jensen@samsung.com>
Tested-by: Dmitry Fomichev <dmitry.fomichev@wdc.com>
Reviewed-by: Dmitry Fomichev <dmitry.fomichev@wdc.com>