wlan: Check SAP_OFFLOADS capability before SAP open

If the ini gEnableSAPAuthOffload is set and firmware doesn't support
SAP_OFFLOADS then effectively driver should not support sap auth
offloads feature.

But from hdd_wlan_startup(), softap is created with sap auth offloads
feature using gEnableSAPAuthOffload only. This leads to out of sync
between firmware and driver thereby causing kernel panic with assert
when driver is expecting auth complete but firmware is giving auth
request notifcation.

To address this, validate firmware SAP_OFFLOADS capability before
softap create.

Change-Id: Ie078a26660ed3823cb26eae8c010511bb5f96410
CRs-Fixed: 2403630