[MIPS] No I/O ports on the DECstation

 There are no I/O ports on the DECstation whatsoever in any configuration 
as neither the CPU nor the peripheral buses used have a concept of such.
Signed-off-by: NMaciej W. Rozycki <macro@linux-mips.org>
Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

arch/mips/Kconfig

@@ -63,6 +63,7 @@ config MACH_DECSTATION
 	bool "DECstations"
 	select BOOT_ELF32
 	select DMA_NONCOHERENT
+	select NO_IOPORT
 	select SYS_HAS_EARLY_PRINTK
 	select IRQ_CPU
 	select SYS_HAS_CPU_R3000
@@ -775,6 +776,9 @@ config MIPS_NILE4
 config MIPS_DISABLE_OBSOLETE_IDE
 	bool
 
+config NO_IOPORT
+	def_bool n
+
 config GENERIC_ISA_DMA_SUPPORT_BROKEN
 	bool
 	select ZONE_DMA