wl12xx/wlcore: move wl1271 struct to wlcore and add ops

wl12xx/wlcore: move wl1271 struct to wlcore and add ops

In order to add chip-specific operations and prepare for future
elements that need to be set by the lower driver, move the wl1271
structure to the wlcore.h file and add an empty placeholder for the
operations structure.

Signed-off-by: Luciano Coelho <coelho@ti.com>