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:
e7b6ef3ac3

Signed-off-by: Jorgen Lundman <lundman@lundman.net>

doc/README.zfs

@@ -0,0 +1,29 @@
+This patch series adds support for ZFS listing and load to u-boot.
+
+To Enable zfs ls and load commands, modify the board specific config file with
+#define CONFIG_CMD_ZFS
+
+Steps to test:
+
+1. After applying the patch, zfs specific commands can be seen
+   in the boot loader prompt using
+        UBOOT #help
+
+        zfsload- load binary file from a ZFS file system
+        zfsls  - list files in a directory (default /)
+
+2. To list the files in zfs pool, device or partition, execute
+        zfsls <interface> <dev[:part]> [POOL/@/dir/file]
+        For example:
+        UBOOT #zfsls mmc 0:5 /rpool/@/usr/bin/
+
+3. To read and load a file from an ZFS formatted partition to RAM, execute
+        zfsload <interface> <dev[:part]> [addr] [filename] [bytes]
+        For example:
+        UBOOT #zfsload mmc 2:2 0x30007fc0 /rpool/@/boot/uImage
+
+References :
+	-- ZFS GRUB sources from Solaris GRUB-0.97
+	-- GRUB Bazaar repository
+
+Jorgen Lundman <lundman at lundman.net> 2012.