ARM: dts: tx6: Remove 'enable-active-low' property

Property 'enable-active-low' does not exist. Only 'enable-active-high' is
valid, and when this property is absent the gpio regulator will act as
active low by default.

So remove the unexisting 'enable-active-low' property.

Currently the GPIO flag is GPIO_ACTIVE_HIGH. In order to make
the dts description accurate, pass the GPIO_ACTIVE_LOW flag instead.

This change is safe because the gpio regulator driver does not take the
GPIO flag polarity into account.

Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Acked-by: Lothar Waßmann <LW@KARO-electronics.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>