[7.2.1] PUA does not select the right machine for Amiga600

Board: Pi3/Pi4/X64

Problem: Amiga600 games like SWIV don't work on Recalbox using PUAE core. I've tested same file on Retroarch (Puae Core) on Windows and it works fine.

With Amiberry works fine.

Problem detected.

For Amiga600 emulator, Recalbox loads games with puae_model = "A500PLUS" parameter, when the correct one is puae_model = "auto"

For this reason, games like SWIV (Amiga600), does not work in Recalbox.