iwlwifi: mvm: fix RSS key sizing

The initialization and copying of the RSS secret key
should not use ARRAY_SIZE as we need to initialize a
dword array, and not a byte array.
Fix also the hook maximum write size to allow writing
a longer table - up to full indirection table size.

Fixes: 43413a97("iwlwifi: mvm: support rss queues configuration command")
Signed-off-by: Sara Sharon <sara.sharon@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>