ARM: dts: sun8i-a83t-tbs-a711: Fix WiFi resume from suspend

Without enabling keep-power-in-suspend, we can't wake the device
up using WOL packet, and the log is flooded with these messages
on resume:

sunxi-mmc 1c10000.mmc: send stop command failed
sunxi-mmc 1c10000.mmc: data error, sending stop command
sunxi-mmc 1c10000.mmc: send stop command failed
sunxi-mmc 1c10000.mmc: data error, sending stop command

So to make the WiFi really a wakeup-source, we need to keep it powered
during suspend.

Fixes: 0e233720 ("arm: dts: sun8i: Add the TBS A711 tablet devicetree")
Signed-off-by: Ondrej Jirman <megous@megous.com>
Signed-off-by: Maxime Ripard <mripard@kernel.org>