comedi: amplc_dio200_common: Conditionally remove I/O port support

In a future patch, the port I/O functions (`inb()`, `outb()`, and
friends will only be declared in the `HAS_IOPORT` configuration option
is enabled.

The amplc_dio200_common module is used by the amplc_dio200 module (for
ISA cards) and the amplc_dio200_pci module (for PCI and PCI Express
cards).  It supports both port I/O and memory-mapped I/O.

Port I/O and memory-mapped I/O is confined to the `dio200___read8()`,
`dio200___read32()`, `dio200___write8()` and `dio200___write32()`
functions.  Conditionally compile two versions of those functions.  If
the `CONFIG_HAS_IOPORT` macro is defined, call either the port I/O or
memory mapped I/O functions depending on the `mmio` member of the
`struct comedi_device`.  If the `CONFIG_HAS_IOPORT` macro is undefined
only call the memory-mapped I/O functions.

Add a run-time check to `amplc_dio200_common_attach()` to return an
error if the device wants to use port I/O when the `CONFIG_HAS_IOPORT`
macro is undefined.

The changes allow the module to be built even if the port I/O functions
have not been declared.

Cc: Arnd Bergmann <[email protected]>
Cc: Niklas Schnelle <[email protected]>
Signed-off-by: Ian Abbott <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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