switch_worker() is the last piece of code that is messy yet it touches virtio/vhost device. Here do a cleanup, so that we will be less painful for later vhost ABI refactoring. The cleanup is straight forward: break long lines, move some code into functions. The last, comment a bit on switch_worker(). Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>