iwlwifi: enlarge number of ucode sections

The maximum number of firmware sections is now 32 instead of 16 for
a000 devices. Set the appropriate define.  Avoid out of bounds access
in case there are more sections than the maximum set by driver.

Make the driver extensible to FW size changes by allocating the
section memory dynamically.

Signed-off-by: Sara Sharon <sara.sharon@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>