cryptsetup: add json-c dependency to host build

cryptsetup: add json-c dependency to host build

Fixes:
http://autobuild.buildroot.net/results/ecf/ecf5d87791e0255c3fce117447105db88749f796/
http://autobuild.buildroot.net/results/384/38462d222f2a893d44de894c30dc1e53d09c377d/
http://autobuild.buildroot.net/results/c29/c2901415345d94ef2135e460f4c78c21ae7ad09a/
... and many more.

Cc: Martin Hicks <mort@bork.org>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>