zfs: Add ZFS filesystem support

U-Boot port is based on sources forked from GRUB-0.97 by Sun in 2004,
which can be found here:
http://src.opensolaris.org/source/xref/onnv/onnv-gate/usr/src/grub/grub-0.97/stage2/zfs-include/zfs.h

Released by Sun for GRUB under the license:
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
  *  the Free Software Foundation; either version 2 of the License, or
  *  (at your option) any later version.

GRUB official releases include ZFS in version:
ftp://alpha.gnu.org/gnu/grub/grub-1.99~rc1.tar.gz

And patched against GRUB Bazaar repository for ashift fixes (4KB HDDs)
more conveniently found at github:
https://github.com/pendor/grub-zfs/commit/e7b6ef3ac3b9685ac4c394c897b1d4221b7381f1

Signed-off-by: Jorgen Lundman <lundman@lundman.net>
diff --git a/include/config_cmd_all.h b/include/config_cmd_all.h
index 73c0558..f434cd0 100644
--- a/include/config_cmd_all.h
+++ b/include/config_cmd_all.h
@@ -87,5 +87,6 @@
 #define CONFIG_CMD_UNZIP	/* unzip from memory to memory	*/
 #define CONFIG_CMD_USB		/* USB Support			*/
 #define CONFIG_CMD_XIMG		/* Load part of Multi Image	*/
+#define CONFIG_CMD_ZFS		/* ZFS Support			*/
 
 #endif	/* _CONFIG_CMD_ALL_H */