[X86] Renamed SHL cost model tests

Matches naming conventions for ASHR/LSHR cost tests

As discussed in D8690.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@249984 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/test/Analysis/CostModel/X86/vshift-cost.ll b/test/Analysis/CostModel/X86/vshift-shl-cost.ll
similarity index 100%
rename from test/Analysis/CostModel/X86/vshift-cost.ll
rename to test/Analysis/CostModel/X86/vshift-shl-cost.ll