qcacld-3.0: Fix check SBS low shared flag
In policy_mgr_get_index_for_ml_sta_sap_hwmode_sbs,
if SBS supported, at least one share type should be
supported.
Fix the missing check of Low share SBS.
Change-Id: I9ab848bab9ae8eb5c9d4bb85022b83be92e4c1e9
CRs-Fixed: 3338956