LibC: Remove errno EEXISTS

I don't know why I had added this. It doesn't seem to be a thing on
either POSIX or linux. This was literally equivalent to EXIST

kernel/klibc/string.cpp

@@ -158,7 +158,6 @@ const char* strerrordesc_np(int error)
 		case ETXTBSY:			return "Text file busy.";
 		case EWOULDBLOCK:		return "Operation would block.";
 		case EXDEV:				return "Cross-device link.";
-		case EEXISTS:			return "File exists";
 		case ENOTBLK:			return "Block device required";
 		case EUNKNOWN:			return "Unknown error";
 	}