gpio: Show inactive GPIOs when explicitly requested

gpio: Show inactive GPIOs when explicitly requested

At present the gpio command only shows GPIOs which are marked as in use.
This makes sense with 'gpio status' since we already have the '-a' flag
to indicate that all GPIOs should be shown. But when a particular GPIO is
requested, it seems better to always display it. At present the request is
simply ignored.

For example if GPIO a10 is not in use, then:

   > gpio status a10

shows nothing, not even the function being used for that GPIO. With this
change, it shows the pin status:

   > gpio status a10
   a10: input: 0 [ ]

Add an extra parameter for this to avoid changing the existing flag
parameter.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Tested-by: Bin Meng <bmeng.cn@gmail.com>
[bmeng: correct the 'gpio' command in the commit message]
Signed-off-by: Bin Meng <bmeng.cn@gmail.com>