According to devctl(4), clients must read events whole; they may not

piece them together from multiple reads().  It's as if /dev/devctl is
a datagram device instead of a stream device.  However, devd's
internal buffer was too small (1025 bytes) to read an entire
ereport.fs.zfs.checksum event (variable, up to ~1300 bytes).  This
commit enlarges the buffer to 8k.

Reviewed by:	imp
Approved by:	ken (mentor)
MFC after:	2 weeks

sbin/devd/devd.h

@@ -53,6 +53,6 @@ int  yyparse(void);
 __END_DECLS
 
 #define PATH_DEVCTL	"/dev/devctl"
-#define DEVCTL_MAXBUF	1025
+#define DEVCTL_MAXBUF	8192
 
 #endif /* DEVD_H */