smb: client: remove redundant pointer 'server'

The pointer 'server' is assigned but never read, the pointer is
redundant and can be removed. Cleans up clang scan build warning:

fs/smb/client/dfs.c:217:3: warning: Value stored to 'server' is
never read [deadcode.DeadStores]

Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Signed-off-by: Steve French <stfrench@microsoft.com>