ARM: dts: am437x-gp-evm: add wilink8 support

enable mmc3 used for wlan and uart3 used for bluetooth

configure the gpios used for wlan and bluetooth controls

add fixed voltage regulator used for wlan power control

Signed-off-by: Eyal Reizer <eyalr@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>