wlcore: remove wl12xx_platform_data

Now that we have wlcore device-tree bindings in place
(for both wl12xx and wl18xx), remove the legacy
wl12xx_platform_data struct, and move its members
into the platform device data (that is passed to wlcore)

Davinci 850 is the only platform that still set
the platform data in the legacy way (and doesn't
have DT bindings), so remove the relevant
code/Kconfig option from the board file (as suggested
by Sekhar Nori)

Since no one currently uses wlcore_spi, simply remove its
platform data support (DT bindings will have to be added
if someone actually needs it)

Signed-off-by: Luciano Coelho <luca@coelho.fi>
Signed-off-by: Eliad Peller <eliad@wizery.com>
Tested-by: Nikita Kiryanov <nikita@compulab.co.il>
Acked-by: Kalle Valo <kvalo@codeaurora.org>
Acked-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>