libregexp: fix assert check for compile1 instruction count

the assert fails for regcompnl(".") as TANY is compiled to
one instruction instead of two when nl == 0.

its not a problem when we end up with less instructions, so
changing the assert condition from == to <= to make sure we
didnt overrun the buffer.

--
cinap

sys/src/libregexp/regcomp.c

@@ -299,7 +299,7 @@ compile(Renode *parsetr, Reprog *reprog, int nl)
 	sub = 0;
 	reinst = (Reinst*)(reprog+1);
 	end = compile1(parsetr, reinst, &sub, nl);
-	assert(reinst + reprog->len == end);
+	assert(end <= reinst + reprog->len);
 	return reinst;
 }