UIO: add PRUSS UIO driver support

This patch implements PRUSS (Programmable Real-time Unit Sub System)
UIO driver which exports SOC resources associated with PRUSS like
I/O, memories and IRQs to user space. PRUSS is dual 32-bit RISC
processors which is efficient in performing embedded tasks that
require manipulation of packed memory mapped data structures and
handling system events that have tight real time constraints. This
driver is currently supported on Texas Instruments DA850, AM18xx and
OMAP-L138 devices.
For example, PRUSS runs firmware for real-time critical industrial
communication data link layer and communicates with application stack
running in user space via shared memory and IRQs.

Signed-off-by: Pratheesh Gangadhar <pratheesh@ti.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Hans J. Koch <hjk@hansjkoch.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>