x32: xfail elf/tst-platform-1 [BZ #22363]

Xfail elf/tst-platform-1 on x32 since kernel passes i686 in AT_PLATFORM.
See https://sourceware.org/bugzilla/show_bug.cgi?id=22363



Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
Reviewed-by: Sam James <sam@gentoo.org>