staging: comedi: s626: don't dereference insn->data

commit b655c2c4782ed3e2e71d2608154e295a3e860311 upstream.

`s626_enc_insn_config()` is incorrectly dereferencing `insn->data` which
is a pointer to user memory.  It should be dereferencing the separate
`data` parameter that points to a copy of the data in kernel memory.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Reviewed-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>