dt-bindings: power: supply: bq24735: reverse the polarity of ac-detect

The ACOK pin on the bq24735 is active-high, of course meaning that when
AC is OK the pin is high. However, all Tegra dts files have incorrectly
specified active-high even though the signal is inverted on the Tegra
boards. This has worked since the Linux driver has also inverted the
meaning of the GPIO. Fix this situation by simply specifying in the
bindings what everybody else agrees on; that the ti,ac-detect-gpios is
active on AC adapter absence.

Signed-off-by: Peter Rosin <peda@axentia.se>
Acked-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Sebastian Reichel <sre@kernel.org>