comedi: Move "comedi_8254.h" to <linux/comedi/comedi_8254.h>

comedi: Move "comedi_8254.h" to <linux/comedi/comedi_8254.h>

Some of the header files in "drivers/comedi/drivers/" are common enough
to be useful to out-of-tree comedi driver modules.  Using them for
out-of-tree module builds is hampered by the headers being outside the
"include/" directory so it is desirable to move them.

There are about a couple of dozen or so Comedi device drivers that use
the "comedi_8254" module to add timers based on the venerable 8254
Programmable Interval Timer chip.  The macros and declarations to use
that module are in the "comedi_8254.h" header file in the comedi
"drivers" directory.  Move it into "include/linux/comedi/".

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Link: https://lore.kernel.org/r/20211117120604.117740-5-abbotti@mev.co.uk
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>