wl1271: read fem manufacturer value from nvs

We should read the fem manufacturer value from the NVS, so we can modify it
easily and use a consistent value throughout the configuration.  Previously
we had to set the FEM value in the NVS and in the driver's initialization
parameters.  This patch removes the latter.

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