wl1271: Add support for NVS files with 5GHz band parameters

This patch adds support for NVS files with 5GHz band parameters. The change
is done in a backward compatible manner - if 11a is not enabled in the driver,
the driver will allow also old NVS files to be loaded.

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>