[DCCP]: Remove duplicate test for CloseReq

This removes a redundant test for unexpected packet types. In dccp_rcv_state_process
it is tested twice whether a DCCP-server has received a CloseReq (Step 7):

 * first in the combined if-statement,
 * then in the call to dccp_rcv_closereq().

The latter is necesssary since dccp_rcv_closereq() is also called from
__dccp_rcv_established().

This patch removes the duplicate test.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>