open64: Force O_LARGEFILE on all architectures

When running tests on OpenRISC which has 32-bit wordsize but 64-bit
timesize it was found that O_LARGEFILE is not being set when calling
open64.  For 64-bit architectures the O_LARGEFILE flag is generally
implied by the kernel according to force_o_largefile.  However, for
32-bit architectures this is not done.

For this patch we unconditionally now set the O_LARGEFILE flag for
open64 class syscalls as there is no harm in doing so.

Tested on the OpenRISC the build works and timezone/tst-tzset passes
which was failing before.  I would expect this also would fix arc.

Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>