kconfig: kill off GENERIC_IO option

The GENERIC_IO option is set for every architecture except tile and score
as those define NO_IOMEM. The option only controls visibility of
CONFIG_MTD which doesn't appear to be necessary for any reason, so let's
just remove GENERIC_IO.

Signed-off-by: Rob Herring <[e-mail]>
Cc: Jeff Dike <[e-mail]>
Cc: Richard Weinberger <[e-mail]>
Cc: David Woodhouse <[e-mail]>
Cc: Brian Norris <[e-mail]>
Cc: Boris Brezillon <[e-mail]>
Cc: Marek Vasut <[e-mail]>
Cc: Cyrille Pitchen <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]
Cc: [e-mail]
Acked-by: Richard Weinberger <[e-mail]>
Acked-by: Boris Brezillon <[e-mail]>
Signed-off-by: Richard Weinberger <[e-mail]>

arch/um/Kconfig.common

···
 	select HAVE_DEBUG_KMEMLEAK
 	select GENERIC_IRQ_SHOW
 	select GENERIC_CPU_DEVICES
-	select GENERIC_IO
 	select GENERIC_CLOCKEVENTS
 	select HAVE_GCC_PLUGINS
 	select TTY # Needed for line.c

drivers/mtd/Kconfig

···
 menuconfig MTD
 	tristate "Memory Technology Device (MTD) support"
-	depends on GENERIC_IO
 	help
 	  Memory Technology Devices are flash, RAM and similar chips, often
 	  used for solid state file systems on embedded devices. This option

lib/Kconfig

···
 	bool
 	select GENERIC_PCI_IOMAP
 
-config GENERIC_IO
-	bool
-	default n
-
 config STMP_DEVICE
 	bool