This reverts commit 63379c13.

It broke userspace and adding more checking is not needed.
Even checking if a syscall would access memory in page zero doesn't
makes sense since it may lead to some syscalls returning -EFAULT
where we would return other error codes on other platforms.
In summary, just drop this change and return to always return 1.
Signed-off-by: NHelge Deller <deller@gmx.de>