Revert "first version of Smtdeleg/Sstcfg additions"

Author: bcstrongx

src/priv-csrs.adoc

@@ -288,8 +288,6 @@ Supervisor count overflow.
 
 |`0x5A8` |SRW |`scontext` |Supervisor-mode context register.
 
-|`XXX` |SRW |`stselect` |Supervisor Trigger Select register.
-
 //4+^|Supervisor Resource Management Configuration
 //|`0x181` |SRW |`srmcfg` |Supervisor Resource Management Configuration.