The code gen for f32 to i32 bitcast is not currently the most efficient;
this patch removes some unneccessary instructions gerneated.
Differential revision: https://reviews.llvm.org/D100782
This patch generates the vinsw, vinsd, vinsblx, vinshlx, vinswlx, vinsdlx,
vinsbrx, vinshrx, vinswrx and vinsdrx instructions for vector insertion on P10.
Differential Revision: https://reviews.llvm.org/D94454