gpio: Add a function to obtain a GPIO vector value

We can use GPIOs as binary digits for reading 'strapping' values. Each GPIO
is assigned a single bit and can be set high or low on the circuit board. We
already have a legacy function for reading these values. Add one that
supports driver model.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
2 files changed