Remove unneeded reloads

[vladimirradosavljevic]

After #494, we can get the following pattern (taken from the M3B3 tests/yul/semantic/for.yul) generated in the regalloc:

	add	r1, r0, stack-[3]               ; 32-byte Folded Spill
	add	stack-[3], r0, r1               ; 32-byte Folded Reload

In this case, reload is not needed since the previous instruction spills the same register to the same stack slot as in the reload.
Since there is an optimization to remove unneeded spills if the previous instruction is reload from the same stack slot (StackSlotColoring::RemoveDeadStores), create a similar optimization to remove unneeded reloads.