[AArch64][MachineScheduler] Set no side effect for movprfx

The movprfx is a vector copy, so it doesn't access memory. Set the
value of hasSideEffects 0 to avoid return true for the hasUnmodeledSideEffects(),
which will block the machine scheduler which load/store instructions.

Reviewed By: paulwalker-arm
Differential Revision: https://reviews.llvm.org/D140680