[source] brcm47xx: fix initramfs image build error

[LEDE Commits]

nbd pushed a commit to source.git, branch master:
https://git.lede-project.org/a07c4977ac19535cc5fd8187c354de00181382bb

commit a07c4977ac19535cc5fd8187c354de00181382bb
Author: Felix Fietkau <nbd at nbd.name>
AuthorDate: Fri Nov 25 13:10:38 2016 +0100

    brcm47xx: fix initramfs image build error
    
    Signed-off-by: Felix Fietkau <nbd at nbd.name>
---
 target/linux/brcm47xx/image/Makefile | 1 +
 1 file changed, 1 insertion(+)

diff --git a/target/linux/brcm47xx/image/Makefile b/target/linux/brcm47xx/image/Makefile
index 44fdd73..2b8142a 100644
--- a/target/linux/brcm47xx/image/Makefile
+++ b/target/linux/brcm47xx/image/Makefile
@@ -138,6 +138,7 @@ define Device/Default
 	KERNEL := kernel-bin
 	IMAGE_NAME = $$(IMAGE_PREFIX)-$$(1).$$(2)
 	KERNEL_NAME = vmlinux.lzma
+	KERNEL_INITRAMFS_NAME = vmlinux-initramfs.lzma
 	FILESYSTEMS := $(FS_64K)
 	IMAGES := trx
 	IMAGE/trx := append-rootfs | trx-with-loader