[AArch64] Fix UB about shift amount exceeds data bit-width
Fixes an UB caught by sanitizer. The shift amount might be larger than 32 so the operand should be 1ULL.
In this patch, we replace the original expression with existing API with uint64_t type.
Reviewers: eli.friedman, rengolin
Reviewed By: rengolin
Subscribers: rengolin, javed.absar, llvm-commits, kristof.beyls
Differential Revision: https://reviews.llvm.org/D44234