/dev/port: don't compile file operations without CONFIG_DEVPORT

/dev/port: don't compile file operations without CONFIG_DEVPORT

In the future inb() and friends will not be available when compiling
with CONFIG_HAS_IOPORT=n so we must only try to access them here if
CONFIG_DEVPORT is set which depends on HAS_IOPORT.

Co-developed-by: Arnd Bergmann <arnd@kernel.org>
Signed-off-by: Arnd Bergmann <arnd@kernel.org>
Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
Link: https://lore.kernel.org/r/20240404114917.3627747-2-schnelle@linux.ibm.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>