ir3: fix spill/reload split src/dst regs
When splitting spills/reloads into to multiple separate spills/reloads, the src/dst registers where not adjusted. This caused the separate instructions too all refer to the same register.
I'm a bit surprised that this didn't cause any issues before, especially since I found this accidentally in a CTS test (that still passed).
Interestingly, this also seems to give a small performance boost in renderpass time (about 0.3% on some d3d11 traces). Presumably because it prevents a lot of (sy)
being emitted for consecutive ldp
s to the same register.