UIO: Add the User IO core code

This interface allows the ability to write the majority of a driver in
userspace with only a very small shell of a driver in the kernel itself.
It uses a char device and sysfs to interact with a userspace process to
process interrupts and control memory accesses.

See the docbook documentation for more details on how to use this
interface.

From: Hans J. Koch <hjk@linutronix.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Benedikt Spranger <b.spranger@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/Kconfig b/drivers/Kconfig
index 7916f4b..ae01d86 100644
--- a/drivers/Kconfig
+++ b/drivers/Kconfig
@@ -84,4 +84,5 @@
 
 source "drivers/kvm/Kconfig"
 
+source "drivers/uio/Kconfig"
 endmenu