arm64: dts: clearfog-gt-8k: fix USB regulator gpio polarity

The fixed regulator driver ignores the gpio flags, so this change has
no practical effect in the current implementation. Fix it anyway to
correct the hardware description.

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>