Added missing description of changes to the hedeleg register (riscv#466)

This should fix riscv#465

src/hypervisor-integration.adoc

@@ -50,6 +50,12 @@ VU-mode as described in xref:section_cheri_disable[xrefstyle=short].
 
 The reset value is 0.
 
+[#hedeleg,reftext="hedeleg"]
+=== Hypervisor Exception Delegation Register (hedeleg)
+
+Bit 28 of <<hedeleg>> now refers to a valid exception and so can be used to
+delegate CHERI exceptions to virtual supervisor mode.
+
 [#htval,reftext="htval"]
 === Hypervisor Trap Value Register (htval)