[PATCH] Fix typo in Clang test arm-cortex-cpus.c

[Gabor Ballabas]

I am working on a patch that accepts only existing subtarget names in the triple.
Right now every string that starts with armv, armebv, thumbv or thumbebv is accepted.
This test failed with my work-in-progress patch.

http://reviews.llvm.org/D5823