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>
diff --git a/include/config_cmd_all.h b/include/config_cmd_all.h
index 124d51f..e82f642 100644
--- a/include/config_cmd_all.h
+++ b/include/config_cmd_all.h
@@ -48,6 +48,7 @@
 #define CONFIG_CMD_IMI		/* iminfo			*/
 #define CONFIG_CMD_IMLS		/* List all found images	*/
 #define CONFIG_CMD_IMMAP	/* IMMR dump support		*/
+#define CONFIG_CMD_IO		/* Access to X86 IO space	*/
 #define CONFIG_CMD_IRQ		/* irqinfo			*/
 #define CONFIG_CMD_ITEST	/* Integer (and string) test	*/
 #define CONFIG_CMD_JFFS2	/* JFFS2 Support		*/