systemd-boot: update systemd-bootaarch64.efi path

poky updated systemd from 256 to 257 which changed
the build time path.

Signed-off-by: Mikko Rapeli <mikko.rapeli@linaro.org>
Signed-off-by: Ross Burton <ross.burton@arm.com>

meta-arm/recipes-core/systemd/systemd-boot-uefi-secureboot.inc

@@ -1,6 +1,6 @@
 inherit sbsign
 
-SBSIGN_TARGET_BINARY = "${B}/src/boot/efi/systemd-boot${EFI_ARCH}.efi"
+SBSIGN_TARGET_BINARY = "${B}/src/boot/systemd-boot${EFI_ARCH}.efi"
 
 do_compile:append() {
     do_sbsign