Fix compiler warning, optimizing along the way

[bill88t]

Fixes new gcc compiler warnings, rewriting the same thing but in a plain better way.

main.cpp: In function ‘bool _Z9mergeBootv.part.0()’:
main.cpp:1493:43: error: ‘%s’ directive output may be truncated writing up to 557 bytes into a region of size 5 [-Werror=format-truncation=]
 1493 |         snprintf(buffer, sizeof(buffer), "%s", chip);
      |                                           ^~
......
 1534 |                 chipType = convertChipType(chip + 2);
      |                            ~~~~~~~~~~~~~~~~~~~~~~~~~