wl1271: Remove outdated SPI functions

With the change to the new firmware, there was a change to firmware memory
partitioning. Along with that change, the translation of all partitions was
unified, and separate functions for reg and mem access became unnecessary.

Cleanup the unnecessary functions.

Signed-off-by: Juuso Oikarinen <juuso.oikarinen@nokia.com>
Reviewed-by: Luciano Coelho <luciano.coelho@nokia.com>
Signed-off-by: Luciano Coelho <luciano.coelho@nokia.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>