doc: extend installation section for SNOW3G/KASUMI

SNOW3G and KASUMI SW libraries encrypt buffers
assuming that they are padded to a specific block size.
This behaviour can be changed to avoid buffer overflow,
by modifying the Makefile of these libraries.
Therefore, the Installation section in the SNOW3G and
KASUMI documentation has been extended, to document
this case.

Signed-off-by: Pablo de Lara <pablo.de.lara.guarch@intel.com>
Acked-by: Declan Doherty <declan.doherty@intel.com>