target/mips: Fix MIPS64 MFC0 UserLocal on BE host

Using MFC0 to read CP0_UserLocal uses tcg_gen_ld32s_tl, however
CP0_UserLocal is a target_ulong. On a big endian host with a MIPS64
target this reads and sign extends the more significant half of the
64-bit register.

Fix this by using ld_tl to load the whole target_ulong and ext32s_tl to
sign extend it, as done for various other target_ulong COP0 registers.

Fixes: d279279e ("target-mips: implement UserLocal Register")
Signed-off-by: NJames Hogan <james.hogan@imgtec.com>
Cc: Yongbok Kim <yongbok.kim@imgtec.com>
Cc: Aurelien Jarno <aurelien@aurel32.net>
Cc: Petar Jovanovic <petar.jovanovic@imgtec.com>
Reviewed-by: NYongbok Kim <yongbok.kim@imgtec.com>
Signed-off-by: NYongbok Kim <yongbok.kim@imgtec.com>

target/mips/translate.c

@@ -5144,8 +5144,9 @@ static void gen_mfc0(DisasContext *ctx, TCGv arg, int reg, int sel)
             goto cp0_unimplemented;
         case 2:
             CP0_CHECK(ctx->ulri);
-            tcg_gen_ld32s_tl(arg, cpu_env,
+            tcg_gen_ld_tl(arg, cpu_env,
                           offsetof(CPUMIPSState, active_tc.CP0_UserLocal));
+            tcg_gen_ext32s_tl(arg, arg);
             rn = "UserLocal";
             break;
         default: