m68k: Let GENERIC_IOMAP depend on HAS_IOPORT

In a future patch HAS_IOPORT=n will disable inb()/outb() and friends at
compile time. With that choosing dynamically between I/O port and MMIO
access via GNERIC_IOMAP will not work. So only select GENERIC_IOMAP when
HAS_IOPORT is selected.

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>
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Link: https://lore.kernel.org/r/20240403122851.38808-2-schnelle@linux.ibm.com


Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>