crypto: inside-secure - Add fw_little_endian option

This is to add fw_little_endian option, which can
be used for platform which firmware is using little-endian
(instead of big-endian).

Signed-off-by: Peter Harliman Liem <pliem@maxlinear.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>