unbreak zfs module build on sparc64

[Tobias Ulmer <tobiasu%tmux.org@localhost>]

ZFS has a conflicting definition of delay() and tries to hide it by
defining __HIDE_DELAY.

sparc64 (and sparc from the looks of it) lack the required #ifndef
dance:

diff --git a/sys/arch/sparc64/include/param.h b/sys/arch/sparc64/include/param.h
index fe09b57cbf55..77d706dd8bab 100644
--- a/sys/arch/sparc64/include/param.h
+++ b/sys/arch/sparc64/include/param.h
@@ -224,8 +224,10 @@ extern int nbpg, pgofset, pgshift;
 #ifdef _KERNEL
 #ifndef _LOCORE
 
+#ifndef __HIDE_DELAY
 extern void	delay(unsigned int);
 #define	DELAY(n)	delay(n)
+#endif /* __HIDE_DELAY */
 
 #ifdef	__arch64__
 /* If we're using a 64-bit kernel use 64-bit math */