tests/sys_crypto: exclude some test for 8 and 16 bit arch
tests/sys_crypto: exclude some test for 8 and 16 bit arch

The tests doesn't work when length_encoding is above the maximum uint16
value.

Also add a set that checks the right error code is returned with too
small length_encoding.

basilfx/RIOT,miri64/RIOT,kaspar030/RIOT,smlng/RIOT,RIOT-OS/RIOT,kYc0o/RIOT,aeneby/RIOT,OlegHahm/RIOT,RIOT-OS/RIOT,kYc0o/RIOT,authmillenon/RIOT,authmillenon/RIOT,RIOT-OS/RIOT,yogo1212/RIOT,josephnoir/RIOT,authmillenon/RIOT,miri64/RIOT,authmillenon/RIOT,yogo1212/RIOT,mtausig/RIOT,miri64/RIOT,smlng/RIOT,OTAkeys/RIOT,josephnoir/RIOT,toonst/RIOT,basilfx/RIOT,jasonatran/RIOT,josephnoir/RIOT,toonst/RIOT,toonst/RIOT,smlng/RIOT,kaspar030/RIOT,miri64/RIOT,toonst/RIOT,x3ro/RIOT,kaspar030/RIOT,authmillenon/RIOT,jasonatran/RIOT,OlegHahm/RIOT,jasonatran/RIOT,kYc0o/RIOT,mtausig/RIOT,OlegHahm/RIOT,x3ro/RIOT,x3ro/RIOT,mtausig/RIOT,jasonatran/RIOT,yogo1212/RIOT,kYc0o/RIOT,aeneby/RIOT,RIOT-OS/RIOT,OTAkeys/RIOT,OlegHahm/RIOT,aeneby/RIOT,aeneby/RIOT,OTAkeys/RIOT,authmillenon/RIOT,mtausig/RIOT,yogo1212/RIOT,kaspar030/RIOT,ant9000/RIOT,OlegHahm/RIOT,aeneby/RIOT,smlng/RIOT,josephnoir/RIOT,ant9000/RIOT,kaspar030/RIOT,basilfx/RIOT,yogo1212/RIOT,basilfx/RIOT,ant9000/RIOT,jasonatran/RIOT,mtausig/RIOT,kYc0o/RIOT,RIOT-OS/RIOT,OTAkeys/RIOT,x3ro/RIOT,OTAkeys/RIOT,miri64/RIOT,smlng/RIOT,ant9000/RIOT,toonst/RIOT,basilfx/RIOT,x3ro/RIOT,yogo1212/RIOT,josephnoir/RIOT,ant9000/RIOT