qcacld-3.0: Finish removing CONFIG_MCL_REGDB

Change I12af832d81815277ec6014ff5047bf960f01534a ("qcacld-3.0: Replace
CONFIG_MCL_REGDB with CONFIG_REG_CLIENT") replaced all usage of
CONFIG_MCL_REGDB.

Subsequently Change If2fb00bd2298aa6f43418b3e4694aa995887b4f3
("qcacld-3.0: Add qcs40x.snoc.perf_defconfig") added a new
instance. Since this instance is pointless, remove it.

Change-Id: If464eb9f510ded7fe9f2cfac3e16263f35fe3af6
CRs-Fixed: 3489450

configs/qcs40x.snoc.perf_defconfig

@@ -151,7 +151,6 @@ CONFIG_FEATURE_WLAN_RA_FILTERING:= y
 CONFIG_FEATURE_WLAN_LPHB := y
 CONFIG_FEATURE_WLAN_EXTSCAN := n
 CONFIG_160MHZ_SUPPORT := y
-CONFIG_MCL_REGDB := y
 CONFIG_WLAN_OFFLOAD_PACKETS := y
 CONFIG_WLAN_SYNC_TSF := y
 CONFIG_WLAN_SYNC_TSF_PLUS := y