include/image.mk: introduce KERNEL_INITRAMFS_NAME variable

In case if we're interested in generation of non-binary images
(for example if we want images to be valid .elfs - and that's what we
want for ARC now) we have to instruct Device/Build/initramfs target to
use input file with some extension (in case of ARC it will be
essentially .elf).

Otherwise default binary vmlinux-initramfs (without extension) is used and
resulting images then are binaries instead of elfs.

Now having KERNEL_INITRAMFS_NAME variable it's possible to substitute
default $$(KERNEL_NAME)-initramfs with preferred option like
$$(KERNEL_NAME)-initramfs.elf.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Cc: Felix Fietkau <nbd@openwrt.org>
Cc: John Crispin <blogic@openwrt.org>

SVN-Revision: 47403

include/image.mk

@@ -432,6 +432,7 @@ define Device/Init
   KERNEL_IMAGE = $$(KERNEL_PREFIX)$$(KERNEL_SUFFIX)
   KERNEL_INITRAMFS_PREFIX = $$(IMAGE_PREFIX)-initramfs
   KERNEL_INITRAMFS_IMAGE = $$(KERNEL_INITRAMFS_PREFIX)$$(KERNEL_SUFFIX)
+  KERNEL_INITRAMFS_NAME = $$(KERNEL_NAME)-initramfs
   KERNEL_INSTALL :=
   KERNEL_NAME := vmlinux
   KERNEL_SIZE :=
@@ -458,11 +459,11 @@ define Device/Build/initramfs
   $(call Device/Export,$(KDIR)/tmp/$$(KERNEL_INITRAMFS_IMAGE),$(1))
   $$(_TARGET): $(BIN_DIR)/$$(KERNEL_INITRAMFS_IMAGE)
 
-  $(KDIR)/$$(KERNEL_NAME)-initramfs: image_prepare
+  $(KDIR)/$$(KERNEL_INITRAMFS_NAME): image_prepare
   $(BIN_DIR)/$$(KERNEL_INITRAMFS_IMAGE): $(KDIR)/tmp/$$(KERNEL_INITRAMFS_IMAGE)
 	cp $$^ $$@
 
-  $(KDIR)/tmp/$$(KERNEL_INITRAMFS_IMAGE): $(KDIR)/$$(KERNEL_NAME)-initramfs
+  $(KDIR)/tmp/$$(KERNEL_INITRAMFS_IMAGE): $(KDIR)/$$(KERNEL_INITRAMFS_NAME)
 	@rm -f $$@
 	$$(call concat_cmd,$$(KERNEL_INITRAMFS))
 endef