greybus: svc: Remove unused declarations

Commit 84427943 ("greybus: svc: drop legacy-protocol dependency")
removed these implementations but not the declarations.

Signed-off-by: Yue Haibing <yuehaibing@huawei.com>
Link: https://lore.kernel.org/r/20230818124338.37880-1-yuehaibing@huawei.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>