boot/syslinux: install in a sub-dir of $(BINARIES_DIR)

Since syslinux can now install quite a number of files, install
them in a sub-directory of $(BINARIES_DIR) for clarity.

It also aligns it to rpi-firmware, grub2, gummiboot, that install
all of their files in a sub-dir of $(BINARIES_DIR), too.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Romain Naour <romain.naour@openwide.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

boot/syslinux/syslinux.mk

@@ -70,11 +70,11 @@ SYSLINUX_C32 = $(call qstrip,$(BR2_TARGET_SYSLINUX_C32))
 # scattered around everywhere in the build tree.
 define SYSLINUX_INSTALL_IMAGES_CMDS
 	for i in $(SYSLINUX_IMAGES-y); do \
-		$(INSTALL) -D -m 0755 $(@D)/$$i $(BINARIES_DIR)/$${i##*/}; \
+		$(INSTALL) -D -m 0755 $(@D)/$$i $(BINARIES_DIR)/syslinux/$${i##*/}; \
 	done
 	for i in $(SYSLINUX_C32); do \
 		$(INSTALL) -D -m 0755 $(HOST_DIR)/usr/share/syslinux/$${i} \
-				   $(BINARIES_DIR)/$${i}; \
+				   $(BINARIES_DIR)/syslinux/$${i}; \
 	done
 endef