iwlwifi: avoid duplicate sw reset executions in the code

Most of the sw resets in the code are done by one function,
which writes to the relevant CSR.

Use the common function to perform the only reset which was
done separately, redundant to the common code.

Signed-off-by: Golan Ben Ami <golan.ben.ami@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>