iscsid: Push #ifdef ICL_KERNEL_PROXY into cap_ioctl_limits list.

This reduces duplication in the two lists and makes it clearer which
ioctls are needed in the ICL_KERNEL_PROXY case.

Reviewed by: mav
Sponsored by: Chelsio Communications
Differential Revision: https://reviews.freebsd.org/D34927

(cherry picked from commit f0df72273377daf5e1e97b80a4e542362b261a1d)