Kernel: Use Userspace<T> for the chown syscall

Author: https://github.com/bgianfo
Commit: 0db669a9d2
Pull-request: https://github.com/SerenityOS/serenity/pull/3039

Kernel/Syscalls/chown.cpp

@@ -38,7 +38,7 @@ int Process::sys$fchown(int fd, uid_t uid, gid_t gid)
     return description->chown(uid, gid);
 }
 
-int Process::sys$chown(const Syscall::SC_chown_params* user_params)
+int Process::sys$chown(Userspace<const Syscall::SC_chown_params*> user_params)
 {
     REQUIRE_PROMISE(chown);
     Syscall::SC_chown_params params;