rxrpc: remove redundant variables 'sp' and 'did_discard'

rxrpc: remove redundant variables 'sp' and 'did_discard'

Variables 'sp' and 'did_discard' are being assigned,
but are never used, hence they are redundant and can be removed.

fix following warning:

net/rxrpc/call_event.c:165:25: warning: variable 'sp' set but not used [-Wunused-but-set-variable]
net/rxrpc/conn_client.c:1054:7: warning: variable 'did_discard' set but not used [-Wunused-but-set-variable]

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: David Howells <dhowells@redhat.com>