[Detect] Consider nested loop profitable if entry block is not in loop

[Detect] Consider nested loop profitable if entry block is not in loop

In cases where the entry block of a scop was not contained in a loop that was
part of the scop region and at the same time there was a loop surrounding the
scop, we missed to count the loops in the scop and consequently did not consider
the scop profitable. We correct this by only moving to the loop parent, in case
the current loop is loop contained in the scop.

This increases the number of loops in COSMO which we assume to be profitable
from 3974 to 4981.

git-svn-id: https://llvm.org/svn/llvm-project/polly/trunk@311863 91177308-0d34-0410-b5e6-96231b3b80d8