rpi-cmdline: Package is machine-specific

The cmdline.txt file generated by this recipe includes machine-specific
information so we should set PACKAGE_ARCH appropriately.

Signed-off-by: Paul Barker <paul@pbarker.dev>

recipes-bsp/bootfiles/rpi-cmdline.bb

@@ -49,3 +49,5 @@ do_deploy() {
 
 addtask deploy before do_build after do_install
 do_deploy[dirs] += "${DEPLOYDIR}/${BOOTFILES_DIR_NAME}"
+
+PACKAGE_ARCH = "${MACHINE_ARCH}"