iwlwifi: increase command buffer size

Increase the buffer size for commands with "huge"
bit set. This has been recently observed for 6050 cards where
for even with huge bit set few commands were not properly allocated
memory with the command overwriting the buffer allocated for it..
Also add a check to see if command size exceeds the
maximum allowable size.

Signed-off-by: Abhijeet Kolekar <abhijeet.kolekar@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>