mediatek: remove duplicate KERNEL{_INITRAMFS}

mediatek: remove duplicate KERNEL{_INITRAMFS}

Remove duplicate KERNEL/KERNEL_INITRAMFS recipes from filogic.mk,
which are already defined in Device/Default for the mediatek target:

  KERNEL = kernel-bin | lzma | \
    fit lzma $$(KDIR)/image-$$(firstword $$(DEVICE_DTS)).dtb
  KERNEL_INITRAMFS = kernel-bin | lzma | \
    fit lzma $$(KDIR)/image-$$(firstword $$(DEVICE_DTS)).dtb with-initrd

Signed-off-by: Chukun Pan <amadeus@jmu.edu.cn>
Link: https://github.com/openwrt/openwrt/pull/23490
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>