Add ini to set init chain mode for BTC, default value should
be set to the same as macro WLAN_COEX_BTC_CHAIN_MODE_UNSETTLED
that means no need to send init chain mode for BTC to firmware
in wma_vdev_pre_start() process.
Change-Id: I3051a7f8a0c708c7df40d1b95b46e0bfa6892f6c
CRs-Fixed: 2837173