rockchip: dts: rk3399-puma: fix the modelling of BIOS_DISABLE

The fixed regulator for overriding BIOS_DISABLE had been modelling
backwards (i.e. the GPIO polarity and the enable-active-low/high
property had both been inverted), causing the 'regulator' command
to always print/expect 'disabled'/'enabled' backwards.

This fixes the mix-up and models it correctly:
 * the GPIO is low-active
 * the regulator should be enabled (enable-active-high) during
   boot-on initialisation

Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Tested-by: Klaus Goger <klaus.goger@theobroma-systems.com>