brcm63xx: improve image/Makefile

- Use KERNEL_INITRAMFS_SUFFIX for customizing initramfs name.
- Modifying $(PROFILES) is no longer needed.

Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>

target/linux/brcm63xx/image/Makefile

@@ -167,9 +167,8 @@ define Build/redboot-bin
 endef
 
 define Device/Default
-  PROFILES = Default
   KERNEL_DEPENDS = $$(wildcard ../dts/$$(DEVICE_DTS).dts)
-  KERNEL_INITRAMFS_IMAGE = $$(KERNEL_INITRAMFS_PREFIX).elf
+  KERNEL_INITRAMFS_SUFFIX := .elf
   DEVICE_DTS :=
 endef
 DEVICE_VARS += DEVICE_DTS