gostr3411-94: Fix the iteration count for length filling loop.

* cipher/gostr3411-94.c (gost3411_final): Fix loop

The maximum iteration count for filling the l (bit length) array was
incrrectly set to 32 (missed that in u8->u32 refactoring). This was
not resulting in stack corruption, since nblocks variable would be
exausted earlier compared to 8 32-bit values (the size of the array).

• Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>