dt-bindings: pinctrl: drive-strength doesn't default to 2 if unspecified

If the drive-strength isn't specified in the device tree then it
doesn't actually default to 2. Instead, it defaults to whatever the
heck the BIOS left it at. If the BIOS doesn't touch it then that means
it's whatever the heck the initial state of the pin was when the SoC
booted.

Reported-by: Matthias Kaehlcke <mka@chromium.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Matthias Kaehlcke <mka@chromium.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Link: https://lore.kernel.org/r/20220111140519.1.Ie2662d6289af1e9758b14b37149703c846d5f509@changeid


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