[llvm] [Hexagon] Have fast-math-libcalls.ll use the default hexagonv68 cpu (PR #149647)

[Matt Arsenault via llvm-commits]

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@@ -61,15 +61,9 @@ define double @fast_add_f64(double %x, double %y) {
 ; CHECK-LABEL: fast_add_f64:
 ; CHECK:         .cfi_startproc
 ; CHECK-NEXT:  // %bb.0:
-; CHECK-NEXT:    .cfi_def_cfa r30, 8
-; CHECK-NEXT:    .cfi_offset r31, -4
-; CHECK-NEXT:    .cfi_offset r30, -8
-; CHECK-NEXT:    {
-; CHECK-NEXT:     call __hexagon_fast_adddf3
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arsenm wrote:

This no longer uses the libcall defeating the point of the test 

https://github.com/llvm/llvm-project/pull/149647