ARM: dts: exynos: correct fuel gauge interrupt trigger level on GT-I9100

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: 8620cc2f ("ARM: dts: exynos: Add devicetree file for the Galaxy S2")
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20201210212534.216197-1-krzk@kernel.org