Make prefetch.i use pcc instead of ddc in integer mode (#319)

Fixes #318

src/insns/prefetch.i.adoc

@@ -42,7 +42,7 @@ effective address is the sum of the base address specified in `rs1` and the
 sign-extended offset encoded in imm[11:0], where imm[4:0] equals 0b00000, is
 likely to be accessed by an instruction fetch in the near future. The encoding
 is only valid if imm[4:0]=0. The authorising capability for this operation is
-<<ddc>>.
+<<pcc>>.
 
 :prefetch_insn: PREFETCH.I
 :prefetch_perm: <<x_perm>>