dpkg: remove redundant check

function                                             old     new   delta
dpkg_main                                           4008    3991     -17

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/archival/dpkg.c b/archival/dpkg.c
index 7caccef..219512b 100644
--- a/archival/dpkg.c
+++ b/archival/dpkg.c
@@ -1739,7 +1739,6 @@
 	//if (opt & OPT_unpack) ... // -u (--unpack in official dpkg)
 	if (!(opt & OPTMASK_cmd) /* no cmd */
 	 || ((opt & OPTMASK_cmd) & ((opt & OPTMASK_cmd)-1)) /* more than one cmd */
-	 || (!(opt & OPT_list_installed) && !argv[0]) /* - all except -l require argument */
 	) {
 		bb_show_usage();
 	}