target/arm: Fix PC test for LDM (exception return)

Found by inspection: Rn is the base register against which the
load began; I is the register within the mask being processed.
The exception return should of course be processed from the loaded PC.
Signed-off-by: NRichard Henderson <richard.henderson@linaro.org>
Reviewed-by: NPhilippe Mathieu-Daudé <philmd@redhat.com>
Message-id: 20190301202921.21209-1-richard.henderson@linaro.org
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

target/arm/translate.c

@@ -10612,7 +10612,7 @@ static void disas_arm_insn(DisasContext *s, unsigned int insn)
                             } else if (i == rn) {
                                 loaded_var = tmp;
                                 loaded_base = 1;
-                            } else if (rn == 15 && exc_return) {
+                            } else if (i == 15 && exc_return) {
                                 store_pc_exc_ret(s, tmp);
                             } else {
                                 store_reg_from_load(s, i, tmp);