The original patch (https://reviews.llvm.org/D121354) targets x86 and adjusts
the lookahead score of splat loads ad they can be done by the movddup
instruction that combines the load and the broadcast and is cheap to execute.
A similar issue shows up on AArch64. The ld1r instruction performs a broadcast
load and is cheap to execute.
This patch implements the TargetTransformInfo hooks for AArch64.