misc: fix valgrind complaints

misc: fix valgrind complaints

Zero the memory that we pass to the kernel via ioctls so that we never
pass userspace heap/stack garbage around.  This silences valgrind
complaints about uninitialized padding areas.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Chandan Babu R <chandanrlinux@gmail.com>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>