selftests: sparc64: char: Selftest for privileged ADI driver

Add a selftest for the sparc64 privileged ADI driver.  These
tests verify the read(), pread(), write(), pwrite(), and seek()
functionality of the driver.  The tests also report simple
performance statistics:

        Syscall Call    AvgTime AvgSize
                Count   (ticks) (bytes)
        -------------------------------
        read          3  119638    8133
        pread         4  118164    6741
        write         3  339442    8133
        pwrite        4  280134    6741
        seek         10    2919       0
        Pass 8 Fail 0 Xfail 0 Xpass 0 Skip 0 Error 0

Signed-off-by: Tom Hromatka <tom.hromatka@oracle.com>
Reviewed-by: Allen Pais <allen.pais@oracle.com>
Reviewed-by: Shuah Khan (Samsung OSG) <shuah@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>