target-mips: correct DERET instruction

Fix Debug Mode flag clearing, and when DERET is placed between LL and SC
do not make SC fail.

Signed-off-by: Leon Alrae <leon.alrae@imgtec.com>
Reviewed-by: Aurelien Jarno <aurelien@aurel32.net>

target-mips/op_helper.c

@@ -2154,10 +2154,9 @@ void helper_deret(CPUMIPSState *env)
     debug_pre_eret(env);
     set_pc(env, env->CP0_DEPC);
 
-    env->hflags &= MIPS_HFLAG_DM;
+    env->hflags &= ~MIPS_HFLAG_DM;
     compute_hflags(env);
     debug_post_eret(env);
-    env->lladdr = 1;
 }
 #endif /* !CONFIG_USER_ONLY */