x86/ia32-compat: Fix CLONE_SETTLS bitness of copy_thread()

CLONE_SETTLS is expected to write a TLS entry in the GDT for
32-bit callers and to set FSBASE for 64-bit callers.

The correct check is is_ia32_task(), which returns true in the
context of a 32-bit syscall.  TIF_IA32 is set if the task itself
has a 32-bit personality, which is not the same thing.

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Link: http://lkml.kernel.org/r/45e2d0d695393d76406a0c7225b82c76223e0cc5.1424822291.git.luto@amacapital.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>