ARM: dts: iwg23s-sbc: Fix SDHI2 VccQ regulator

ARM: dts: iwg23s-sbc: Fix SDHI2 VccQ regulator

SDR50 isn't working anymore because the GPIO regulator
driver is using descriptors since
commit d6cd33ad7102 ("regulator: gpio: Convert to use descriptors")
which in turn causes the system to use the polarity of the
GPIOs (as specified in the DT) for selecting the states,
but the polarity specified in the DT is wrong.
This patch fixes the regulator DT definition, and that fixes
SDR50.

Fixes: 9eb36b945b5c ("ARM: dts: iwg23s-sbc: Add uSD and eMMC support")
Signed-off-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>