linux-wandboard

iwlagn: use kcalloc when possible for array allocation

As everybody knows kcalloc checks the multiplication is safe and
that we don't run into overflow.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>