standardize "extension" suffix on extensions in priv preface (#1708)

* standardize "extension" suffix on extensions in preface

* italicize unratified extension

src/priv-preface.adoc

@@ -13,24 +13,24 @@ modules:
 |_Machine ISA_ +
 *Smstateen Extension* +
 *Smcsrind/Sscsrind Extension* +
-*Smepmp* +
-*Smcntrpmf* +
+*Smepmp Extension* +
+*Smcntrpmf Extension* +
 *Smrnmi Extension* +
-*Smcdeleg* +
-*Smdbltrp* +
-*Supervisor ISA* +
+*Smcdeleg Extension* +
+*Smdbltrp Extension* +
+_Supervisor ISA_ +
 *Svade Extension* +
 *Svnapot Extension* +
 *Svpbmt Extension* +
 *Svinval Extension* +
 *Svadu Extension* +
-*Sstc* +
-*Sscofpmf* +
-*Ssdbltrp* +
-*Ssqosid* +
+*Sstc Extension* +
+*Sscofpmf Extension* +
+*Ssdbltrp Extension* +
+*Ssqosid Extension* +
 *Hypervisor ISA* +
-*Shlcofideleg* +
-*Svvptc*
+*Shlcofideleg Extension* +
+*Svvptc Extension*
 
 |_1.14_ +
 *1.0* +