Revert "Fix rasberry Pi 64bit firmware overlay inclusion"

This reverts commit 51d6d6c580432435f2b2f95ed35e22a5ecbe9dcb.

That change is no more relevant since the genimage.cfg files are
generated by the commit e37ee5acdc (board/raspberrypi/post-image.sh:
generate genimage config from template if not present), and since the
variant-specific files were dropped off by the commit fc5cdeed72
(board/raspberrypi: drop variant-specific genimage files).

This removes the very last alive piece of change of the commit
51d6d6c580 (Fix rasberry Pi 64bit firmware overlay inclusion); the
commit is fully reverted now.

Signed-off-by: Gaël PORTAY <gael.portay@rtone.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/rpi-firmware/rpi-firmware.mk

@@ -59,12 +59,6 @@ define RPI_FIRMWARE_INSTALL_DTB_OVERLAYS
 	$(INSTALL) -D -m 0644 $(@D)/boot/overlays/overlay_map.dtb $(BINARIES_DIR)/rpi-firmware/overlays/
 	touch $(BINARIES_DIR)/rpi-firmware/overlays/README
 endef
-else
-# Still create the directory, so a genimage.cfg can include it independently of
-# whether _INSTALL_DTB_OVERLAYS is selected or not.
-define RPI_FIRMWARE_INSTALL_DTB_OVERLAYS
-	$(INSTALL) -d $(BINARIES_DIR)/rpi-firmware/overlays
-endef
 endif
 
 # Install prebuilt libraries if RPI_USERLAND not enabled