Possible error in doc comment

If a SCoP is most probably sequential, then it's better to run it on a CPU.
Hence, there's no point in running it on a GPU.

Reviewers: grosser

Subscribers: nemanjai

Tags: #polly

Contributed-by: Singapuram Sanjay <singapuram.sanjay@gmail.com>

Differential Revision: https://reviews.llvm.org/D30864

llvm-svn: 297578