iwmc3200wifi: Remove tx concatenation option

The tx concatenation option works fine now, we no longer need the debugging
option of disabling concatenation.

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