Fix lockstat:::thread-spin dtrace probe with LOCK_PROFILING

[vangyzen]

Summary

The spinning start time is missing from the calculation due to a
misplaced #endif. Return the #endif where it's supposed to be.

Submitted by: Alexander Alexeev <[e-mail]>
MFC after: 1 week
Sponsored by: Dell EMC Isilon

Test Plan

From the submitter:

Without

dtrace -n 'lockstat:::thread-spin { trace((int64_t)arg1); exit(0); }'
dtrace: description 'lockstat:::thread-spin ' matched 1 probe
CPU     ID                    FUNCTION:NAME
 18  79691                 none:thread-spin     3878139600799

With

dtrace -n 'lockstat:::thread-spin { trace((uint64_t)arg1); exit(0); }'

dtrace: description 'lockstat:::thread-spin ' matched 1 probe
CPU     ID                    FUNCTION:NAME
  3  79618                 none:thread-spin               838