ipw2200: use kmalloc for large local variables

Fixed below compiler warning:

drivers/net/wireless/ipw2x00/ipw2200.c: In function ‘ipw_load_firmware’:
drivers/net/wireless/ipw2x00/ipw2200.c:3260: warning: the frame size of
1168 bytes is larger than 1024 bytes

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