wimax: allow WIMAX_RF_QUERY calls when state is still uninitialized

Until now, calls to wimax_rfkill() will be blocked until the device is
at least past the WIMAX_ST_UNINITIALIZED state, return -ENOMEDIUM when
the device is in the WIMAX_ST_DOWN state.

In parallel, wimax-tools would issue a wimax_rfkill(WIMAX_RF_QUERY)
call right after opening a handle with wimaxll_open() as means to
verify if the interface is really a WiMAX interface [newer kernel
version will have a call specifically for this].

The combination of these two facts is that in some cases, before the
driver has finalized initializing its device's firmware, a
wimaxll_open() call would fail, when it should not.

Thus, change the wimax_rfkill() code to allow queries when the device
is in WIMAX_ST_UNINITIALIZED state.

Signed-off-by: Inaky Perez-Gonzalez <inaky@linux.intel.com>