Kconfig: introduce HAS_IOPORT option and select it as necessary

We introduce a new HAS_IOPORT Kconfig option to indicate support for I/O
Port access. In a future patch HAS_IOPORT=n will disable compilation of
the I/O accessor functions inb()/outb() and friends on architectures
which can not meaningfully support legacy I/O spaces such as s390.

The following architectures do not select HAS_IOPORT:

* ARC
* C-SKY
* Hexagon
* Nios II
* OpenRISC
* s390
* User-Mode Linux
* Xtensa

All other architectures select HAS_IOPORT at least conditionally.

The "depends on" relations on HAS_IOPORT in drivers as well as ifdefs
for HAS_IOPORT specific sections will be added in subsequent patches on
a per subsystem basis.

Co-developed-by: Arnd Bergmann <arnd@kernel.org>
Signed-off-by: Arnd Bergmann <arnd@kernel.org>
Acked-by: Johannes Berg <johannes@sipsolutions.net> # for ARCH=um
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

lib/Kconfig

@@ -92,6 +92,7 @@ config ARCH_USE_SYM_ANNOTATIONS
 config INDIRECT_PIO
 	bool "Access I/O in non-MMIO mode"
 	depends on ARM64
+	depends on HAS_IOPORT
 	help
 	  On some platforms where no separate I/O space exists, there are I/O
 	  hosts which can not be accessed in MMIO mode. Using the logical PIO
@@ -509,6 +510,9 @@ config HAS_IOMEM
 	depends on !NO_IOMEM
 	default y
 
+config HAS_IOPORT
+	bool
+
 config HAS_IOPORT_MAP
 	bool
 	depends on HAS_IOMEM && !NO_IOPORT_MAP