MST pointed out: config change callback is also handled incorrectly
in this driver, it takes a mutex from interrupt context.

Handle config changed by work queue instead.

Cc: Gonglei (Arei) <arei.gonglei@huawei.com>
Cc: Halil Pasic <pasic@linux.ibm.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: zhenwei pi <pizhenwei@bytedance.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>