staging: comedi: amplc_dio200: remove 'has_clk_gat_sce' from subdevice

The `has_clk_gat_sce` member of `struct dio200_subdev_8254` indicates
whether the board has clock and gate source selection registers.  The
same information can be obtained from read-only board layout data so
doesn't need to be set per '8254' counter subdevice.  Eliminate the
member and use the read-only data instead.  The last parameter of
`dio200_subdev_8254_init()` is used to initialize this member, so remove
that parameter as well.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>