vsock: Remove unused function declarations

These are never implemented since introduction in
commit d021c344

 ("VSOCK: Introduce VM Sockets")

Signed-off-by: Yue Haibing <yuehaibing@huawei.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Link: https://lore.kernel.org/r/20230729122036.32988-1-yuehaibing@huawei.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>