Revert "wlan: Provide runtime option to enable or disable rssi threshold (base)"

This reverts commit b95c030a.

RSSI threshold parameters are now user configurable.Below are the
parameters.
THRESHOLD_UNBLACKLIST_HARD_5G
THRESHOLD_UNBLACKLIST_SOFT_5G
THRESHOLD_UNBLACKLIST_HARD_24G
THRESHOLD_UNBLACKLIST_SOFT_24G
THRESHOLD_INITIAL_AUTO_JOIN_ATTEMPT_RSSI_MIN_5G
THRESHOLD_INITIAL_AUTO_JOIN_ATTEMPT_RSSI_MIN_24G

Hence reverting the gerrit

Change-Id: I0d589cd494a488a4618434314e76fefde1275abd
CRs-Fixed: 757958