Fix some compiler warnings

[dotsam]

• Fix syntax of a cast to a uint32
• Remove defines that are already made by the base platform

Cleans up platform.io compile output quite a bit, making it much easier to spot other errors/warnings, of which there is still one, but I'm not sure if it's legitimate, and if so, how to fix it:

src/BlueSCSI.cpp: In function 'void longjmpFromInterrupt(int*, int)':
src/BlueSCSI.cpp:790:1: warning: 'noreturn' function does return
  790 | }
      | ^