Check the firmware response size for responses to the
memory read/write command in debugfs before using it.

Fixes: 2b55f43f ("iwlwifi: mvm: Add mem debugfs entry")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Link: https://lore.kernel.org/r/20230417113648.0d56fcaf68ee.I70e9571f3ed7263929b04f8fabad23c9b999e4ea@changeidSigned-off-by: Johannes Berg <johannes.berg@intel.com>