rpi4: remove armstub and 1G memory limit

The lastest firmware includes the updated armstubs, so no need to
rebuild them in Yocto. (meta-raspberrypi commit 69da331154852f5d62d6cf7a69c4ddb34f5564d0)

RPi kernel commit d5dc848c982dff2e020f294e384447efe6ea6617 mitigates the
DMA issues with memory over 1G, so the total_mem=1024 workaround can be
removed.

arm_64bit is still needed because the firmware doesn't set it
automatically based on the presence of kernel8.img, even though it
should (raspberrypi/firmware#1193)

recipes-bsp/bootfiles/rpi-config_git.bbappend

@@ -18,10 +18,7 @@ do_deploy_append_raspberrypi4-64() {
     tee ${DEPLOYDIR}/bcm2835-bootfiles/config.txt <<EOF
 #### NEWBS CONFIG ####
 dtoverlay=disable-bt
-armstub=armstub8-gic.bin
-enable_gic=1
 arm_64bit=1
-total_mem=1024
 ${@d.getVar('EXTRA_CONFIG_TXT').replace('\\n', '\n').strip()}
 EOF
 }