wifi: iwlwifi: mei: Remove unused flexible-array member in struct iwl_sap_hdr

wifi: iwlwifi: mei: Remove unused flexible-array member in struct iwl_sap_hdr

Remove unused fexible-array member and avoid 14 of the following type of
warnings:

drivers/net/wireless/intel/iwlwifi/mei/sap.h:318:28: warning: structure containing a flexible array member is not at the end of another structure
[-Wflex-array-member-not-at-end]

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Link: https://patch.msgid.link/aK6-usANI1UPtFVo@kspp
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>