ARM: dts: exynos: correct fuel gauge interrupt trigger level on Midas family

The Maxim fuel gauge datasheets describe the interrupt line as active
low with a requirement of acknowledge from the CPU.  The falling edge
interrupt will mostly work but it's not correct.

Fixes: e8614292 ("ARM: dts: Add Maxim 77693 fuel gauge node for exynos4412-trats2")
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20201210212534.216197-3-krzk@kernel.org