iw_cxgb4: Fix potential NULL dereference in c4iw_fill_res_cm_id_entry()

This condition needs to match the previous "if (epcp->state == LISTEN) {"
exactly to avoid a NULL dereference of either "listen_ep" or "ep". The
problem is that "epcp" has been re-assigned so just testing
"if (epcp->state == LISTEN) {" a second time is not sufficient.

Fixes: 116aeb88 ("iw_cxgb4: provide detailed provider-specific CM_ID information")
Signed-off-by: Dan Carpenter <error27@gmail.com>
Link: https://lore.kernel.org/r/Y+usKuWIKr4dimZh@kili


Signed-off-by: Leon Romanovsky <leon@kernel.org>