iwlwifi: mvm: support new shared memory config API

In a000 devices we have 15 fifos, so in the shared memory
config the number of tx fifos in the array was changed
accordingly.
As it is in the middle of the struct, the parsing code needs
to be duplicated.
To minimize the duplication, do not save variables we never
actually use.

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