Rename this file from cx2.c to c2x.c; NFC.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@369035 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/test/Sema/attr-cx2.c b/test/Sema/attr-c2x.c
similarity index 100%
rename from test/Sema/attr-cx2.c
rename to test/Sema/attr-c2x.c