mediatek: mt7623: build lzma fit for bpi-r2

bpi-r2 images are shipped with mainline u-boot which can extract lzma
with no problem.
remove custom kernel recipe to build lzma fit image instead of
uncompressed fit with zboot.

Signed-off-by: Chuanhong Guo <[email protected]>

target/linux/mediatek/image/mt7623.mk

@@ -29,9 +29,6 @@ define Device/bpi_bananapi-r2
   DEVICE_VENDOR := Bpi
   DEVICE_MODEL := Banana Pi R2
   DEVICE_DTS := mt7623n-bananapi-bpi-r2
-  KERNEL_NAME := zImage
-  KERNEL := kernel-bin | fit none $$(DTS_DIR)/$$(DEVICE_DTS).dtb
-  KERNEL_INITRAMFS :=
   DEVICE_PACKAGES := kmod-fs-vfat kmod-nls-cp437 kmod-nls-iso8859-1 kmod-mmc \
 	mkf2fs e2fsprogs kmod-usb-ohci kmod-usb2 kmod-usb3 kmod-ata-ahci-mtk
   UBOOT_TARGET := mt7623n_bpir2