crypto: lrw - Fix big endian support

It turns out that LRW has never worked properly on big endian.
This was never discussed because nobody actually used it that
way.  In fact, it was only discovered when Geert Uytterhoeven
loaded it through tcrypt which failed the test on it.

The fix is straightforward, on big endian the to find the nth
bit we should be grouping them by words instead of bytes.  So
setbit128_bbe should xor with 128 - BITS_PER_LONG instead of
128 - BITS_PER_BYTE == 0x78.

Tested-by: Geert Uytterhoeven <Geert.Uytterhoeven@sonycom.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>