Bluetooth: Modify security level at remote_features event for BT2.0 devices

For non SSP devices, MEDIUM_SECURITY has to be used for pairing. This
can be determined and set while receiving remote supported features
event for BT2.0 devices.

Change-Id: I24558d40be01c4232fff4a871e2b57e390d4128a
CRs-fixed: 345945
Signed-off-by: Prabhakaran Mc <prabhakaranmc@codeaurora.org>