find_and_check_chardev() uses 'opts' member of CharDriverState to
check if the chardev is 'socket' chardev or not, which the opts
will be NULL if We add the chardev by qmp 'chardev-add' command.
All the related info can be found in 'filename' member of CharDriverState,
For tcp socket device, it will be like 'disconnected:tcp:9.61.1.8:9004,server'
or 'tcp:9.61.1.8:9001,server <-> 9.61.1.8:50256', we can simply check it to
identify if it is a tcp socket char device.
Besides, fix this helper function to return -1 while some errors happen.
Signed-off-by: zhanghailiang <address@hidden>