crypto: inside-secure - fix scatter/gather list to descriptor conversion

Fixed issues with the skcipher and AEAD scatter/gather list to engine
descriptor conversion code which caused either too much or too little
buffer space to be provided to the hardware. This caused errors with the
testmgr extra tests, either kernel panics (on x86-EIP197-FPGA) or engine
descriptor errors 0x1, 0x8 or 0x9 (on Macchiatobin e.g. Marvell A8K).
With this patch in place, all skcipher and AEAD (extra) tests pass.

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