qemu-char: convert parallel backend to data-driven creation
Conversion to Error * brings better error messages; before:
qemu-system-x86_64: -chardev id=serial,backend=parallel,path=vl.c: Failed to create chardev
After:
qemu-system-x86_64: -chardev id=serial,backend=parallel,path=vl.c: not a parallel port: Inappropriate ioctl for device
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>