EX-6682 build: add json-c-devel into lustre-dkms.spec.in

EX-6682 build: add json-c-devel into lustre-dkms.spec.in

While installing client DKMS package, json-c-devel package is
required. This patch adds the package requirement into
lustre-dkms.spec.in.

Test-Parameters: trivial

Fixes: fbfd2d0755 ("EX-5176 pcc: use JSON string for trusted.pin xattr")
Signed-off-by: Jian Yu <yujian@whamcloud.com>
Change-Id: I72f7e23a8c1ec9edecfc69b2e8dda758f215b4e2
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/49594
Reviewed-by: Minh Diep <mdiep@whamcloud.com>
Reviewed-by: Feng Lei <flei@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>