gpio: max77620: Use correct unit for debounce times

The gpiod_set_debounce() function takes the debounce time in
microseconds. Adjust the switch/case values in the MAX77620 GPIO to use
the correct unit.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://lore.kernel.org/r/20191002122825.3948322-1-thierry.reding@gmail.com


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>