apm821xx: Fix initramfs image for the Meraki MR24

When gzip is used, our kernel is too large and this causes the ramdisk
to be at the wrong offset. Fix by moving to lzma.

Signed-off-by: Chris Blake <chrisrblake93@gmail.com>

target/linux/apm821xx/image/Makefile

@@ -75,7 +75,7 @@ define Device/mr24
   KERNEL_SIZE := 2048k
   IMAGE_SIZE := 8191k
   KERNEL := kernel-bin | lzma | uImage lzma | MerakiAdd-dtb | MerakiNAND
-  KERNEL_INITRAMFS := copy-file $(KDIR)/vmlinux | gzip | uImage gzip | MerakiAdd-dtb | pad-to 2047k | MerakiAdd-initramfs | MerakiNAND
+  KERNEL_INITRAMFS := copy-file $(KDIR)/vmlinux | lzma | uImage lzma | MerakiAdd-dtb | pad-to 2047k | MerakiAdd-initramfs | MerakiNAND
   IMAGE/sysupgrade.tar := sysupgrade-tar
 endef
 TARGET_DEVICES += mr24