dm: gpio: Enhance gpio command to show only active GPIOs

The GPIO list is very long in many cases and most of them are not used.
By default, show only the GPIOs that are in use, and provide a flag to show
all of them. This makes the 'gpio status' command much more pleasant.

In order to do this, driver model now exposes a method for obtaining the
'function' of a GPIO, which describes whether it is an input or output, for
example. Implementation of this method is optional.

Signed-off-by: Simon Glass <sjg@chromium.org>
dm: gpio: Allow gpio command to adjust GPIOs that are busy

The gpio command mostly relies on gpio_request() and gpio_free() being
nops, in that you can request a GPIO twice. With driver model this is
now implemented correctly, so it fails.

Change the command to deal with a failure to claim the GPIO.

Signed-off-by: Simon Glass <sjg@chromium.org>
dm: sandbox: dts: Add a GPIO bank

Add a bank of GPIOs for sandbox which can be used for testing this
functionality.

Signed-off-by: Simon Glass <sjg@chromium.org>
mpc5xxx: Add stub implementation of cache functions

Some drivers (e.g. net/e1000) reference these functions. So, this
fixes the build of MVBC_P board.

I'm not familiar with the MPC5xxx platform, maybe a full
implementation shall be implemented instead of this stub in the
future.

Signed-off-by: Vasili Galka <vvv444@gmail.com>
Cc: Wolfgang Denk <wd@denx.de>, Marek Vasut <marex@denx.de>
Acked-by: Wolfgang Denk <wd@denx.de>
Merge git://git.denx.de/u-boot-dm