qca-wifi: Set monitor buffer size as 2K for 256M profile

Monitor mode is not supported in 256M profile. Therefore set monitor buffer
size as 2K.

Change-Id: I914ede679363d67566537c1abb9f9f1b599b4d20
CRs-Fixed: 2668071

configs/wlan_cfg/ap_wlan_cfg.config

@@ -33,6 +33,10 @@ ifeq ($(strip ${NO_RX_PKT_HDR_TLV}),1)
 #128 bytes of RX_PKT_HEADER_TLV.
 EXTRA_CFLAGS += -DRX_DATA_BUFFER_SIZE=1792
 EXTRA_CFLAGS += -DRX_DATA_BUFFER_ALIGNMENT=0
+ifeq ($(strip ${QCA_LOWMEM_CONFIG}),1)
+EXTRA_CFLAGS += -DRX_MONITOR_BUFFER_SIZE=1792
+EXTRA_CFLAGS += -DRX_MONITOR_BUFFER_ALIGNMENT=0
+endif
 endif
 
 EXTRA_CFLAGS += -DWLAN_PSOC_MAX_VDEVS=60