Abbreviate softdep lock names.

[markj]

Summary

The softdep lock names are unusually long and tend to stick out in lock
profiling reports. Abbreviate them to keep consistent with our
conventional style.

Test Plan

This is how it looks without the change:

Count indv cuml rcnt     nsec Lock                   Caller                                                                                   
-------------------------------------------------------------------------------                                                               
 8676  31%  31% 0.00    10307 pmap pv list           _rw_wlock_cookie+0xbc     
 7961  28%  59% 0.00    54853 vm object              _rw_wlock_cookie+0xbc                                                                    
 6112  22%  80% 0.00    20783 tcpinp                 _rw_wlock_cookie+0xbc     
 5519  19% 100% 0.00     6301 Per-Filesystem Softdep Lock _rw_wlock_cookie+0xbc                                                               
   73   0% 100% 0.00     2857 bufobj interlock       _rw_wlock_cookie+0xbc                                                                    
    2   0% 100% 0.00      300 tidhash                _rw_wlock_cookie+0xbc                                                                    
-------------------------------------------------------------------------------

[mckusick]

This request is entirely reasonable.