speakup: add HAS_IOPORT dependency for SPEAKUP_SERIALIO

speakup: add HAS_IOPORT dependency for SPEAKUP_SERIALIO

In a future patch HAS_IOPORT=n will result in inb()/outb() and friends
not being declared. SPEAKUP_SERIALIO thus needs to depend on HAS_IOPORT.

Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
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/20230522105049.1467313-34-schnelle@linux.ibm.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>