qcacld-3.0: Allow roam invoke while FASTREASSOC

While handling userspace-directed re-association, driver
checks for flag "supplicant_disabled_roaming" before sending
roam invoke command after connection. Currently, the value of
supplicant_disabled_roaming is getting updated by value comes
through vendor command QCA_WLAN_VENDOR_ATTR_ROAMING_POLICY.
In case if roaming does not get enabled using vendor command
in __wlan_hdd_cfg80211_set_fast_roaming, driver rejects
fast re-association cmd. This leads to roaming failure.

Fix is to allow roam invoke command irrespective of flag
"supplicant_disabled_roaming" and send csr_roam_offload_scan
with reason REASON_SUPPLICANT_DISABLED_ROAMING instead of
REASON_DISCONNECTED while processing FASTREASSOC command.

Change-Id: Iee55fff8dd9445a2fb2b96a244f59a763f207dd5
CRs-Fixed: 2408861