Turn off opportunistic key caching (OKC) in firmware based on
"OkcEnabled" parameter in WCNSS_qcom_cfg.ini.
It is enabled by default and can be turned off with value 0.
Remove FEATURE_WLAN_OKC compilation option because OKC is always
compiled in for cld3.0. Remove underlying empty routine
cb_notify_set_okc_feature_enabled().
CRs-Fixed: 1057181
Change-Id: I174e860abef0532d62517635fe56927d8c3c9fd3