btrfs: fix 64bit compat send ioctl arguments not initializing version member

When the send protocol versioning was added in 5.16 e77fbf99
("btrfs: send: prepare for v2 protocol"), the 32/64bit compat code was
not updated (added by 2351f431 ("btrfs: fix send ioctl on 32bit with
64bit kernel")), missing the version struct member. The compat code is
probably rarely used, nobody reported any bugs.

Found by tool https://github.com/jirislaby/clang-struct .

Fixes: e77fbf99

 ("btrfs: send: prepare for v2 protocol")
CC: stable@vger.kernel.org # 6.1+
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>