[LV] Vectorizer should adjust trip count in profile information

Summary: Vectorized loop processes VFxUF number of elements in one iteration thus total number of iterations decreases proportionally. In addition epilog loop may not have more than VFxUF - 1 iterations. This patch updates profile information accordingly.

Reviewers: hsaito, Ayal, fhahn, reames, silvas, dcaballe, SjoerdMeijer, mkuper, DaniilSuchkov

Reviewed By: Ayal, DaniilSuchkov

Subscribers: fedor.sergeev, hiraditya, rkruppe, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D67905