Fix Thumb2 ldrd/strd disassembly.

Change-Id: Ie75aeab5b970640e90e567621ac45ce1a3a7c377
diff --git a/disassembler/disassembler_arm.cc b/disassembler/disassembler_arm.cc
index 65f2383..db51fab 100644
--- a/disassembler/disassembler_arm.cc
+++ b/disassembler/disassembler_arm.cc
@@ -427,9 +427,9 @@
           args << Rt << "," << Rd << ", [" << Rn;
           const char *sign = U ? "+" : "-";
           if (P == 0 && W == 1) {
-            args << "], #" << sign << imm8;
+            args << "], #" << sign << (imm8 << 2);
           } else {
-            args << ", #" << sign << imm8 << "]";
+            args << ", #" << sign << (imm8 << 2) << "]";
             if (W == 1) {
               args << "!";
             }