ARM: dts: dra72-evm-common: Add wilink8 wlan support

Wilink8 module is a combo wireless connectivity card based
on Texas Instrument's wl18xx solution.

Add support for the wlan capabilities of this module by muxing
the relevant mmc lines, and setting the required device-tree
data.

Signed-off-by: Eyal Reizer <eyalr@ti.com>
Signed-off-by: Hari Nagalla <hnagalla@ti.com>
[nsekhar@ti.com: drop WLAN_EN pinmux. It should be done by bootloader.
                 Also, some commit message adjustments]
Signed-off-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>