realtek: rtl839x: enable driver for virtual mtd_concat devices in config

Enable the driver for the rtl839x target. It's required at least for
Netgear GS750E

Signed-off-by: Davide Fioravanti <[email protected]>

target/linux/realtek/rtl839x/config-5.10

@@ -151,6 +151,7 @@ CONFIG_MTD_SPLIT_EVA_FW=y
 CONFIG_MTD_SPLIT_FIRMWARE=y
 CONFIG_MTD_SPLIT_TPLINK_FW=y
 CONFIG_MTD_SPLIT_UIMAGE_FW=y
+CONFIG_MTD_VIRT_CONCAT=y
 CONFIG_NEED_DMA_MAP_STATE=y
 CONFIG_NEED_PER_CPU_KM=y
 CONFIG_NET_DEVLINK=y

target/linux/realtek/rtl839x/config-5.15

@@ -154,6 +154,7 @@ CONFIG_MTD_SPLIT_EVA_FW=y
 CONFIG_MTD_SPLIT_FIRMWARE=y
 CONFIG_MTD_SPLIT_TPLINK_FW=y
 CONFIG_MTD_SPLIT_UIMAGE_FW=y
+CONFIG_MTD_VIRT_CONCAT=y
 CONFIG_NEED_DMA_MAP_STATE=y
 CONFIG_NET_DEVLINK=y
 CONFIG_NET_DSA=y