crypto: inside-secure: back out parts of earlier HMAC update workaround

This patch backs out some changes done with commit 082ec2d4 -
"add support for HMAC updates" as that update just works around the
issue for the basic tests by providing twice the amount of buffering,
but this does not solve the case of much larger data blocks such as
those performed by the extra tests.
This is in preparation of an actual solution in the next patch(es),
which does not actually require any extra buffering at all.

Signed-off-by: Pascal van Leeuwen <pvanleeuwen@verimatrix.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>