Add console command to access io space registers

Provide u-boot console functions to access IO space registers. A no
thrills implementation, accessing one register at a time.

For example:
    boot > iod 80
    0080: 00000094
    boot > iod.w 80
    0080: 0094
    boot > iod.b 80
    0080: 94
    boot > iow.b 0x80 12
    boot > iod 0x80
    0080: 00000012

Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
Signed-off-by: Simon Glass <sjg@chromium.org>
4 files changed