iwlwifi: move rx_page_order into transport

iwlwifi: move rx_page_order into transport

That way it isn't needed in hw_params, which
is shared data. It also isn't really what we
should configure in the transport, that is
better just 4k/8k, so configure a bool and
derive the page order in the transport. This
also means the transport doesn't need access
to the module parameter any more.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>