iwmc3200wifi: Add wifi-wimax coexistence mode as a module parameter

Wifi and wimax coexistence mode is set by wifi at boot time. There can be
several modes, defined by priority tables. User space components can decide
which one to select by writing to /sys/module/iwmc3200wifi/parameters/wiwi
with this patch, before bringing the interface up.

Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>