CLEANUP: config: drop unused setting CONFIG_HAP_INLINE_FD_SET

CONFIG_HAP_INLINE_FD_SET was introduced in 1.3.3 and dropped in 1.3.9
when the pollers were reworked, let's remove it.
diff --git a/include/common/config.h b/include/common/config.h
index 9d12c8e..9d7bf88 100644
--- a/include/common/config.h
+++ b/include/common/config.h
@@ -42,11 +42,4 @@
 #endif
 #endif
 
-/* CONFIG_HAP_INLINE_FD_SET
- * This makes use of inline FD_* macros instead of calling equivalent
- * functions. Benchmarks on a Pentium-M show that using functions is
- * generally twice as fast. So it's better to keep this option unset.
- */
-//#undef  CONFIG_HAP_INLINE_FD_SET
-
 #endif /* _COMMON_CONFIG_H */