cmd: ubi: remove unreachable code

It does not make sense to check if argc < 2 a second time, especially after
accessing argv[1].

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
diff --git a/cmd/ubi.c b/cmd/ubi.c
index a12ac70..c511a2f 100644
--- a/cmd/ubi.c
+++ b/cmd/ubi.c
@@ -472,12 +472,8 @@
 	if (argc < 2)
 		return CMD_RET_USAGE;
 
-	if (strcmp(argv[1], "detach") == 0) {
-		if (argc < 2)
-			return CMD_RET_USAGE;
-
+	if (strcmp(argv[1], "detach") == 0)
 		return ubi_detach();
-	}
 
 	if (strcmp(argv[1], "part") == 0) {
 		const char *vid_header_offset = NULL;