[mlir] parallel loop tiling optimization for loops with static bounds

Summary: The patch optimizes the tiling of parallel loops with static bounds if the number of loop iterations is an integer multiple of the tile size.

Reviewers: herhut, ftynse, bondhugula

Reviewed By: herhut, ftynse

Subscribers: bondhugula, mehdi_amini, rriddle, jpienaar, shauheen, antiagainst, nicolasvasilache, arpith-jacob, mgester, lucyrfox, aartbik, liufengdb, stephenneuendorffer, Joonsoo, grosul1, frgossen, Kayjukh, jurahul, msifontes

Tags: #mlir

Differential Revision: https://reviews.llvm.org/D82003