boot/syslinux: prepare to install non-core images

Currently, we hard-code the path to the images we install, and
expect them to be from the core/ sub-dir.

Not all images we can install are located in core/. For example,
the efi boot images (to come later) are not located in core/.

Prepare the upcoming installation of extlinux by not expecting
images be in core/.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Thomas Lundquist <lists@zelow.no>
Cc: Frank Hunleth <fhunleth@troodon-software.com>
Tested-by: Frank Hunleth <fhunleth@troodon-software.com>
Tested-by: Romain Naour <romain.naour@openwide.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

boot/syslinux/syslinux.mk

@@ -28,12 +28,12 @@ define SYSLINUX_INSTALL_TARGET_CMDS
 	$(TARGET_MAKE_ENV) $(MAKE) -C $(@D) INSTALLROOT=$(HOST_DIR) install
 endef
 
-SYSLINUX_IMAGES-$(BR2_TARGET_SYSLINUX_ISOLINUX) += isolinux.bin
-SYSLINUX_IMAGES-$(BR2_TARGET_SYSLINUX_PXELINUX) += pxelinux.bin
+SYSLINUX_IMAGES-$(BR2_TARGET_SYSLINUX_ISOLINUX) += core/isolinux.bin
+SYSLINUX_IMAGES-$(BR2_TARGET_SYSLINUX_PXELINUX) += core/pxelinux.bin
 
 define SYSLINUX_INSTALL_IMAGES_CMDS
 	for i in $(SYSLINUX_IMAGES-y); do \
-		$(INSTALL) -D -m 0755 $(@D)/core/$$i $(BINARIES_DIR)/$$i; \
+		$(INSTALL) -D -m 0755 $(@D)/$$i $(BINARIES_DIR)/$${i##*/}; \
 	done
 endef