Minor style cleanup

We prefer 'while (0)' to 'while(0)' according to grep and stlye(9)'s
space after keyword rule. Remove a few stragglers of the latter.
Many of these usages were inconsistent within the file.

MFC After:		3 days
Sponsored by:		Netflix

sys/sys/event.h

@@ -62,7 +62,8 @@
 	};					\
 } while (0)
 #else /* Pre-C99 or not STDC (e.g., C++) */
-/* The definition of the local variable kevp could possibly conflict
+/*
+ * The definition of the local variable kevp could possibly conflict
  * with a user-defined value passed in parameters a-f.
  */
 #define EV_SET(kevp_, a, b, c, d, e, f) do {	\