ARM: dts: am335x-sancloud-bbe-extended-wifi: New devicetree

Add support for the SanCloud BBE Extended WiFi board which shares common
hardware with other BBE varients. Compared to the vanilla BBE, this
particular model:

  * adds a WiFi+Bluetooth module connected via SDIO and UART.

  * drops the HDMI encoder, barometer and accelerometer.

Signed-off-by: Paul Barker <paul.barker@sancloud.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>