CTL: Validate IOCTL parameters.

It was possible to cause kernel panic by passing too large args_len
or non-NULL result_nvl.

Though since the /dev/cam/ctl device is accessible only by root and
used only by limited number of tools it was not a big problem.

PR: 266115
PR: 266136
Reported by: Robert Morris <rtm@lcs.mit.edu>
MFC after: 1 week

(cherry picked from commit 0586be48a97c5af50ba4f578d33211f81cc57016)