sandbox: Fix pinmux warnings with non-test devicetrees

sandbox: Fix pinmux warnings with non-test devicetrees

The sandbox pinmux driver is used in the non-test devicetree as well as
the test one. I didn't realize this when I modified the driver for
tests, and so broke the regular use case (which only resulted in
warnings). First, making the pinmux and the UART group available
pre-relocation to avoid ENODEV errors. Then, convert the pin groups and
functions to the new style, adding onewire group as well.

Fixes: 7f0f1806e3a ("test: pinmux: Add test for pin muxing")
Closes: https://source.denx.de/u-boot/u-boot/-/issues/2
Signed-off-by: Sean Anderson <seanga2@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>