Illumos #3522

3522 zfs module should not allow uninitialized variables
Reviewed by: Sebastien Roy <seb@delphix.com>
Reviewed by: Adam Leventhal <ahl@delphix.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Approved by: Garrett D'Amore <garrett@damore.org>

References:
  https://www.illumos.org/issues/3522
  illumos/illumos-gate@d5285cae91

Ported-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>

Porting notes:

1. ZFSOnLinux had already addressed many of these issues because of
   its use of -Wall. However, the manner in which they were addressed
   differed. The illumos fixes replace the ones previously made in
   ZFSOnLinux to reduce code differences.

2. Part of the upstream patch made a small change to arc.c that might
   address zfsonlinux/zfs#1334.

3. The initialization of aclsize in zfs_log_create() differs because
   vsecp is a NULL pointer on ZFSOnLinux.

4. The changes to zfs_register_callbacks() were dropped because it
   has diverged and needs to be resynced.

module/zfs/sa.c

@@ -679,7 +679,8 @@ sa_build_layouts(sa_handle_t *hdl, sa_bulk_attr_t *attr_desc, int attr_count,
 	int buf_space;
 	sa_attr_type_t *attrs, *attrs_start;
 	int i, lot_count;
-	int hdrsize, spillhdrsize = 0;
+	int hdrsize;
+	int spillhdrsize = 0;
 	int used;
 	dmu_object_type_t bonustype;
 	sa_lot_t *lot;