ksmbd: Remove unused functions

ksmbd_rpc_rap() was added in 2021 as part of
commit 0626e664 ("cifsd: add server handler for central processing and
tranport layers")

ksmbd_vfs_posix_lock_wait_timeout() was added in 2021 as part of
commit f4415848 ("cifsd: add file operations")

both have remained unused.

Remove them.

Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>