samples: common: mcumgr_bt_ota_dfu: Adjust defaults

Adjust defaults to reduce RAM

Signed-off-by: Jamie McCrae <jamie.mccrae@nordicsemi.no>

Author: nordicjm

samples/common/mcumgr_bt_ota_dfu/Kconfig

@@ -49,7 +49,7 @@ config IMG_ERASE_PROGRESSIVELY
 if MCUMGR_TRANSPORT_BT_REASSEMBLY
 
 config MCUMGR_TRANSPORT_NETBUF_SIZE
-	default 2475
+	default 1230
 
 config MCUMGR_GRP_OS_MCUMGR_PARAMS
 	default y
@@ -114,13 +114,13 @@ config NCS_SAMPLE_MCUMGR_BT_OTA_DFU_SPEEDUP
 if NCS_SAMPLE_MCUMGR_BT_OTA_DFU_SPEEDUP
 
 config BT_L2CAP_TX_MTU
-	default 498 if BT_HCI_HOST
+	default 247 if BT_HCI_HOST
 
 config BT_BUF_ACL_TX_SIZE
 	default 251
 
 config BT_BUF_ACL_RX_SIZE
-	default 502
+	default 251
 
 config BT_CTLR_DATA_LENGTH_MAX
 	default 251 if HAS_BT_CTLR