[AArch64][GlobalISel] Fix the LegalityPredicate for lowerIf for G_LOAD/G_STORE
Currently, Legalizer is trying to lower G_LOAD with a vector type
that has more than two elements due to the incorrect LegalityPredicate.
This patch fixes the issue by removing the multiplication by 8
as MemDesc.Size already contains the size in bits.
Reviewers: dsanders, aemerson
Reviewed By: dsanders
Subscribers: rovka, javed.absar, kristof.beyls, llvm-commits
Differential Revision: https://reviews.llvm.org/D53679