Revert "Increase length allowed for device-id." to merge better version
committed to FreeBSD head.

This reverts commit eadfae922e963e01d40db44f2391e72fc0e421e5.

Ticket: #5230
Increase CTL_DEVID_LEN from 16 to 64 bytes.

SPC-4 recommends T10 vendor ID based LUN ID was created by concatenating
product name and serial number (and istgt follows that).  But product name
is 16 bytes long by itself, so 16 bytes total length is clearly not enough
to fit both.

To keep compatibility with existing configurations, pad short device IDs
to old length of 16, same as before.

This change probably breaks CTL user-level ABI, so control tools should
be rebuilt after this change.

Ticket:	#5230

(cherry picked from commit 6ec07a92b2e7c38913bdd23c3757ccbba2ba257b)