s526: don't dereference insn->data

s526: don't dereference insn->data

`s526_gpct_insn_config()` and `s526_gpct_winsn()` are incorrectly
dereferencing `insn->data` which is a pointer to user memory.  They
should be using the separate `data` pointer that points to a copy of the
data in kernel memory.  Fix them.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>