virtio-serial: support custom the virtio serial device name

[CV-Bowen]

Summary

By setting config CONFIG_DRIVERS_VIRTIO_SERIAL_NAME to "ttyXX0;ttyXX1;..." to customize the virtio serial name.

For example: If CONFIG_DRIVERS_VIRTIO_SERIAL_NAME="ttyBT;ttyTest0;ttyTest1", virtio-serial will register three uart devices with names: "/dev/ttyBT", "/dev/ttyTest0", "/dev/ttyTest1" to the VFS.

nsh> ls dev /dev: console null telnet ttyBT ttyS0 ttyTest0 ttyTest1 zero

Impact

VirtIO-Serial

Testing

Test with arm64 nsh