uboot-mediatek: fixes defconfig typo for UniFi 6 LR

CONFIG_CMD_MTDPART does not exist, fix it.

Fixes: e9ad412 ("uboot-mediatek: add build for Ubiquiti Networks UniFi 6 LR")
Signed-off-by: Chukun Pan <[email protected]>

package/boot/uboot-mediatek/patches/412-add-ubnt-unifi-6-lr.patch

@@ -64,7 +64,7 @@
 +CONFIG_CMD_LINK_LOCAL=y
 +# CONFIG_CMD_MBR is not set
 +CONFIG_CMD_MTD=y
-+CONFIG_CMD_MTDPART=y
++CONFIG_CMD_MTDPARTS=y
 +# CONFIG_CMD_PCI is not set
 +CONFIG_CMD_SF_TEST=y
 +CONFIG_CMD_PING=y