iwlwifi: mvm: fix RSS config command

The hash mask is a bitmap, so we should use BIT() on
the enum values.

Signed-off-by: Sara Sharon <sara.sharon@intel.com>
Fixes: 43413a97 ("iwlwifi: mvm: support rss queues configuration command")
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>