crypto: tgr192 - fix unaligned memory access

Fix an unaligned memory access in tgr192_transform() by using the
unaligned access helpers.

Fixes: 06ace7a9 ("[CRYPTO] Use standard byte order macros wherever possible")
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>