tools/testing/selftests/epoll/test_epoll.c: fix build
tools/testing/selftests/epoll/test_epoll.c: fix build

Latest Linus head run of "make selftests" in the tools directory failed
with references to undefined variables.  Reference was to
'write_thread_data' which is the name of a struct that is being used, not
the variable itself.  Change reference so it points to the variable.

Signed-off-by: Daniel Hazelton <3f2777fb6edd13b8456640315a252ccc178f3594@gmail.com>
Cc: "Paton J. Lewis" <719e5b711d4b4162829db3fd4ba0ac74ed6993e6@adobe.com>
Signed-off-by: Andrew Morton <5c1e68b099950c134891f0b6e179498a8ebe9cf9@linux-foundation.org>
Signed-off-by: Linus Torvalds <69652caca27c8b940640ad396ab71f93cacec34f@linux-foundation.org>

KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs