fix linux build: use consistent case when including header files

[driftregion]

Building fails on linux because the file system is case-sensitive. #include FlashOS.H" does not result in "FlashOS.h" being included.

Compiling ../../../source/wiznet/W7500/FlashDev.c
../../../source/wiznet/W7500/FlashDev.c:17:10: fatal error: FlashOS.H: No such file or directory
   17 | #include "FlashOS.H"
      |          ^~~~~~~~~~~
compilation terminated.
make: *** [Makefile:223：build/FlashDev.o] 错误 1
progen.tools.gccarm ERROR       Project: errors build failed with the status: projectfiles/make_gcc_arm/w7500/Makefile