qcacld-3.0: enable macro for monitor mode rssi conversion

enable DP_MON_RSSI_IN_DBM macro for monitor mode rssi
conversion.

Change-Id: Idd54f8658611a766ade17700b38904c90d1d4241
CRs-Fixed: 2848120

Kbuild

@@ -3313,6 +3313,7 @@ cppflags-y += -DENABLE_HAL_REG_WR_HISTORY
 cppflags-y += -DDP_RX_DESC_COOKIE_INVALIDATE
 cppflags-y += -DMON_ENABLE_DROP_FOR_MAC
 cppflags-y += -DPCI_LINK_STATUS_SANITY
+cppflags-y += -DDP_MON_RSSI_IN_DBM
 endif
 
 # Enable Low latency optimisation mode