[AMDGPU][GlobalISel] Update legalizer for G_ABS, G_SMIN, G_SMAX, G_UMIN, G_UMAX

There is no need to increase the size of odd sized vectors if they are
going to be scalarized by a different rule.

Patch by: Acim Maravic

Differential Revision: https://reviews.llvm.org/D155865