Update eventfd.c

[TusharNaugain]

Better Thread Safety:
Uses atomic operations for the counter
Proper memory barriers and synchronization
Lock-free implementation where possible

Enhanced Features:
Added EFD_SEMAPHORE support
Better flag handling and validation
Proper cleanup in close operation

Improved Error Handling:
More comprehensive input validation
Better handling of edge cases
Memory allocation failure handling

[tbodt]

This appears to be AI generated

[tbodt]

To be clear, we appreciate you trying to help. But generating a pull request with ChatGPT is not the way to do it, as the result here is so far below the quality of human written code that it's not worth trying to review it. This is also trying to make too many changes in one commit. Overall, despite ChatGPT output looking kind of professional, it looks highly unprofessional to just submit it - anyone could do that! show your own skills!